Java Software Solutions, 9th edition John Lewis Test Bank by Ace Test Banks

Java Software Solutions, 9th edition By John Lewis

Email: richard@qwconsultancy.com

Java Software Solutions, 9e (Lewis/Loftus) Chapter 1 Introduction TRUE/FALSE 1. All information is stored in the computer using binary numbers. ANS: T The computer is a digital device meaning that it stores information in one of two states using binary. We must determine then how to represent meaningful information (such as a name or a program instruction or an image) in binary. 2. Java is an object-oriented programming language. ANS: T Java is classified as a high-level programming language but it is also classified as an object-oriented programming language because it allows the programmer to implement data structures as classes. 3. System.out.print is used in a program to denote that a documentation comment follows. ANS: F Documentation comments follow // marks or are embedded between */ and */. System.out.print is an instruction used to output a message to the screen (the Java console window). 4. Java byte codes are directly executable whereas Java source code is not. ANS: F Neither Java source code nor Java byte codes are executable. Both must be compiled or interpreted into machine code. Java byte codes are useful however in that they are machine-independent but semi-compiled code that allows your Java code to be transmitted over the Internet and executed on another computer even if that other computer is a completely different type. 5. The Java compiler is able to find all programmer errors. ANS: F The Java compiler can find syntax errors but cannot find either logical errors (errors that are caused because of poor logic in writing the program) or run-time errors (errors that arise during the execution of the program). 6. Java is a case-sensitive language which means Current, CURRENT, and current will all reference the same identifier. ANS: F

Java is case sensitive which means that Current, CURRENT, and current will all be recognized as different identifiers. This causes problems with careless programmers who do not spell an identifier consistently in terms of upper and lower case characters. 7. Code placed inside of comments will not be compiled and, therefore, will not execute. ANS: T The compiler discards comments; therefore, any code inside a comment is discarded and is not compiled. Your executable program consists only of the code that is compiled. 8. The word Public is a reserved word. ANS: F public is a reserved word, but since Java is case sensitive, Public differs from public and therefore Public is not a reserved word.

9. Reserved words in Java can be redefined by the programmer to mean something other than their original intentions. ANS: F Java reserved words cannot be redefined. 10. In a Java program, dividing by zero is a syntax error. ANS: F Dividing by 0 is not detected at compile time, and because a computer cannot divide by 0, this is a runtime error. 11. In a Java program, dividing by zero is a syntax error. ANS: F Dividing by 0 is not detected at compile time, and because a computer cannot divide by 0, this is a runtime error. 12. During translation, the compiler puts its output (the compiled Java program) into ROM. ANS: F ROM stands for read-only-memory. The compiled output (the byte codes) may be placed into RAM (writable random access memory) or into a file (on your hard drive, for example). 13. Objects are defined by a class that describes the characteristics common to all instances of the class. ANS: T An object is an instance of a class. And, the purpose of a class is to describe these common characteristics.

14. Inheritance is a form of software reuse. ANS: T Inheritance allows us to capitalize on the similarities among various kinds of classes that have a common base (parent) class. Thus we reuse the base class each time a class inherits from it. 15. Polymorphism is the idea that we can refer to multiple types of related objects in consistent ways. ANS: T Polymorphism allows us to use the same name for similar behaviors that occur among diverse and possibly unrelated objects. For example, to "open" may refer to a file, or to a device, or to a communications line, etc. The same term, "open," is being used even though the objects that are being opened are quite different. 16. In Java, identifiers may be of any length up to a limit determined by the compiler. ANS: F Java (and Java compilers) do not limit the length of the identifiers you use. Identifiers may be as long as you wish. Good programming practice, however, will limit the lengths of the identifiers you create.

MULTIPLE CHOICE 1. A Java program is best classified as a. b. c. d. e.

hardware software storage processor input

ANS: B Programs are classified as software to differentiate them from the mechanisms of the computer (hardware). Storage and the processor are two forms of hardware while input is the information that the program processes. 2. Six bits can be used to represent __________ distinct items or values. a. b. c. d. e.

6 20 24 32 64

ANS: E With n bits, we can represent 2^n different values. 2^6 = 64. 3. When executing a program, the processor reads each program instruction from a. secondary memory (storage) b. the Internet

c. registers stored in the processor d. main memory e. Any of these ANS: D The program is first loaded from secondary memory into main memory before it is executed so that the processor is not slowed down by reading each instruction. This idea of executing programs stored in memory is called the Stored Program Computer and was pioneered by John Von Neumann in the 1940s. 4. Which memory capacity is the largest? a. b. c. d. e.

1,500,000,000,000 bytes 100 gigabytes 3,500,000 kilobytes 10 terabytes 12,000,000 megabytes

ANS: E We convert each of these capacities to bytes (rounding off) to compare them. The value in A remains the same, 1 1/2 trillion bytes. The value in B is 100 billion bytes. The value in C is 3 1/2 billion bytes. The value in D is 10 trillion bytes. The answer in E is 12 trillion bytes. 5. Binary numbers are composed entirely of a. b. c. d. e.

0s 1s 0s and 1s any digits between 0 and 9 0s, 1s, and 2s

ANS: C Binary is base 2. In Mathematics, numbers in base n are composed entirely of digits between 0 and n1. 6. Volatility is a property of a. b. c. d. e.

RAM ROM disk software computer networks

ANS: A

Volatility means that the contents of memory are lost if the electrical power is shut off. This is true of RAM (Random Access Memory), but not ROM (Read Only Memory) or disk. Software and computer networks are not forms of memory. 7. The ability to directly obtain a stored item by referencing its address is known as a. b. c. d.

random access sequential access read-only access fetch access

e. volatility ANS: A Random access is meant to convey the idea that accessing any item is equally easy, and that any item is retrievable based solely on its address. Random access is the form of access used by both RAM and ROM memory. Disk access, called direct access, is a similar idea, and direct and random access are sometimes referred to synonymously. Sequential access is used by tape. 8. Which phase of the fetch-decode-execute cycle might use a circuit in the arithmetic-logic unit? a. b. c. d. e.

fetch decode execute during fetch or execute, but not decode any of the phases

ANS: C The fetch phase retrieves (fetches) the next program instruction from memory. The decode phase determines which circuit(s) needs to be used to execute the instruction. The instruction is executed during the execute phase. If the instruction is either an arithmetic operation (like add or multiply) or a logical operation (like comparing two values), then it is carried out by the ALU. 9. In order for a computer to be accessible over a computer network, the computer needs its own a. b. c. d. e.

MODEM communication line network address packet router

ANS: C In order to differentiate between the computers on a network, each is given its own, unique, network address. In this way, a message intended for one computer can be recognized by that computer through the message's destination address. A MODEM is a device that is used to allow a computer to communicate to another computer over a telephone line. A communication line is the network media itself. A packet is a collection of data that is sent over a network. A router is a hardware device used to take a message from one network and move it to another based on the message's destination address. 10. For a computer to communicate over the Internet, it must use a. b. c. d. e.

the TCP protocol the IP protocol the combined TCP/IP protocol the Ethernet protocol the ARPANET protocol

ANS: C IP is the Internet Protocol, but the TCP (Transmission Control Protocol) also must be used because it handles such problems as how to piece together packets of the same message that arrive out of order. Ethernet is a LAN protocol, which might be used in addition to TCP/IP in some networks, but it is not needed to communicate over the Internet. There is no such thing as the ARPANET protocol. 11. A URL (Uniform Resource Locator) specifies the address of a a. computer on any network

b. c. d. e.

computer on the Internet local area network (LAN) on the Internet a document or other type of file on the Internet a Java program on the Internet

ANS: D URLs are used to locate documents (or other types of files such as an image or sound file) anywhere on the Internet. A URL contains the address of the LAN or WAN and the specific computer from which the file is to be retrieved; it specifies the file's address, not just the computer's address. 12. It is important to dissect a problem into manageable pieces before trying to solve the problem because a. most problems are too complex to be solved as a single, large activity b. most problems are solved by multiple people and it is easy to assign each piece to a separate person c. ir is easier to integrate small pieces of a program into one program than it is to integrate one big chunk of code into one program d. the first solution may not solve the problem correctly e. All of these ANS: A Any interesting problem will be too complex to solve easily as a single activity. By decomposing the problem, we can build small solutions for each piece and then integrate the pieces. Answer D is true, but it is not the reason why we will break a problem into pieces. 13. Once we have implemented a solution, we are not done with the problem because a. b. c. d.

the solution may not be the best (most efficient) the solution may have errors and need testing and fixing the solution may, at a later date, need revising to handle new specifications the solution may, at a later date, need revising because of new programming language features e. All of these ANS: E A program should not be considered as a finished product until we are reasonably assured that it is efficient and error-free. Further, it is common that programs require modification in the future because of a change to specifications or a change to the language or computer running the program. 14. Java is an example of a(n) a. b. c. d. e.

machine language Assembly language high-level language fourth generation language both high-level and fourth generation language

ANS: E While Java was created during the fourth generation, it is clearly also a high-level language. Machine language is the executable language of a machine, with programs written in 1s and 0s only. Assembly language uses mnemonics. Fourth generation languages are tools wrapped inside of programs so that the user has the flexibility to write some code to executed from within the program.

15. Of the following, which statement is not true regarding Java as a programming language? a. Java is a relatively recent language; it was introduced in 1995. b. Java is a language whose programs do not require translating into machine language before they are executed. c. Java is an object-oriented language. d. Java is a language that embraces the idea of writing programs to be executed with the World Wide Web. e. All of these are true ANS: B All languages require translation into machine language. The other statements are all true about Java. 16. Comments should a. b. c. d. e.

rephrase all the code to explain it in English be insightful and explain the intention of an instruction or block of code only be included with code that is difficult to understand be used to define variables that have hard to understand names All of these

ANS: B Comments should not rephrase in English what an instruction says, but instead should explain what that instruction is doing in relation to the program. Introductory programmers often have difficult explaining their code and wind up stating the obvious in their comments. While answer D is partially correct, it is not entirely true even though all variables should have comments that explain their use. 17. The main method for a Java program is defined by a. b. c. d. e.

public static main() public static main(String[] args); public static main(String[] args) private static main(String[] args) The main method could be defined by all of these except B

ANS: C In A, the parameter is missing. The parameters are defined later in the text, but in effect, they allow the user to run the program and include some initial arguments if the program calls for it. In B, the semicolon at the end of the statement is not allowed. In D, private instead of public would make the program non-executable by anyone and thus makes the definition meaningless. 18. What does the following line of Java code do? //System.out.println("Hello"); a. b. c. d. e.

nothing cause Hello to be output cause a syntax error cause ("Hello") to be output There is no way to tell without executing the code.

ANS: A The characters // denote the beginning of a comment. The comment is not compiled and so, nothing would happen when this code is executed.

19. What comment might be added to explain the following instruction? System.out.println("Hello World"); a. b. c. d. e.

// prints "Hello World" to the screen //prints a message //used to demonstrate an output message // // meaningless instruction

ANS: C Comments in A and B state the obvious while the comments in D and E are meaningless. The comment in C explains why the instruction appears in the program. 20. Which character belowis not allowed in an identifier? a. b. c. d. e.

$ _ 0 1 ^

ANS: E Java identifiers can consist of any letter, digit, $ or _ as long as the identifier starts with a letter or _. ^ is not a legal character. 21. Which of the following is not syntactically legal in Java? a. b. c. d. e.

System.out.println("Hi"); public class Foo s t a t i c main(String[] args) {} only A is legally valid; all the others are illegal

ANS: C The Java compiler would not recognize "s t a t i c" as "static" because the Java compiler treats white space (blanks) as separators between entities. The other statements are all legal, including "{}" which is a block that happens to have no statements within it. 22. Which of the following is a legal Java identifier? a. b. c. d. e.

i class 1likeclass! idon'tlikeclass i-like-class

ANS: A Java identifiers cannot have the characters !, ' or - in them so answers C, D and E are wrong. The word class is a reserved word in Java and cannot be used as an identifier. The identifier i is perfectly legal although it is not necessarily a good identifier since it is not descriptive of its use. 23. A unique aspect of Java that allows code compiled on one machine to be executed on a machine with a different hardware platform is Java's

a. b. c. d. e.

bytecodes syntax use of objects use of exception handling All of these

ANS: A The translation process for a Java program is to first compile it into bytecodes, which are architecturally neutral (that is, they can be used no matter what the architectural platform is). To execute the program, the bytecodes must be further compiled by a Java compiler or interpreted by a Java Virtual Machine. 24. Java is similar in syntax to which of the following high-level languages? a. b. c. d. e.

Pascal Ada C++ FORTRAN BASIC

ANS: C The creators of Java decided to use syntax similar to C++ so that C++ programmers could easily learn Java. Variable declarations, assignment statements, loops, selection statements and comments are among the features that have nearly identical syntax. There are many differences however, so don't assume that any C or C++ programmer will easily or instantly be able to program in Java. 25. An error in a program that results in the program outputtinh $100 instead of the correct answer, $250, is a a. b. c. d. e.

compiler error syntax error run-time error logical error snafu

ANS: D While this is an error, programmers classify the type of error in order to more easily solve the problem. Syntax errors are caught by the compiler and the program cannot run without fixing all syntax errors. Run-time errors arise during program execution and cause the program to stop running. Logical errors are errors whereby the program can run to completion, but gives the wrong answer. If the result should have been $250, then the logic of the program is wrong since it output $100. A snafu is a term expressing a messed up situation in combat and should not be used by respectable programmers! 26. Which of the following is true regarding Java syntax and semantics? a. A Java compiler can determine if you have followed proper syntax but not proper semantics. b. A Java compiler can determine if you have followed proper semantics but not proper syntax. c. A Java compiler can determine if you have followed both proper syntax and proper semantics. d. A Java compiler cannot determine if you have followed either proper syntax or proper semantics.

e. A Java compiler can determine if you have followed proper syntax but not proper semantics only if you follow the Java naming convention rules. ANS: A Compilers for all languages have the ability to detect syntax errors because improper use of the syntax leads to situations where the compilers cannot translate the code properly. However, compilers are unable to follow the semantics of a program because this requires a degree of understanding what the program is intended to do and computers have no sense of understanding (at least at this point). 27. Using Java naming convention, which of the following would be a good variable name for the current value of a stock? a. b. c. d. e.

curstoval theCurrentValueOfThisStock currentStockVal csv current

ANS: C Java allows long variable names but the programmer must find a good compromise between an excessive long name (as with B) and names too short to understand their use (A and D). The name current possibly might be reasonable if there are no other "current" values being referenced in the program. 28. Which of the following is a legal Java identifier? a. b. c. d. e.

1ForAll oneForAll one/4/all 1_4_all 1forall

ANS: B Java identifiers cannot start with a number (so the answers in A, D and E are illegal) and cannot include the / character, so the answer in C is illegal. 29. A color image is broken down into individual pixels (points), each of which is represented by a. b. c. d.

a 1 for white and a 0 for black 3 values denoting the intensity of red, green, and blue in the image a single number indicating the intensity of color between white and black two numbers, where one indicates where the color is between white and black and the other denotes the brightness e. None of these; it is not possible to represent color ANS: B Black and white images are stored using 0s and 1s while color images are stored using three values, one each for the degree of red, the degree of blue, and the degree of green. 30. Which of the following characters does not need to have an associated closing character in a Java program? a. { b. (

c. [ d. < e. All of these require closing characters ANS: D { is used to open a block, and so } is needed to close the block. ( is used to open an expression and so ) is needed to close an expression. [ is used to start an array index so ] is needed to close the array index. < is "less than" and > is "greater than" and these are not needed together, so < requires no closing character. 31. Mistyping println as printn will result in a. b. c. d. e.

a syntax error a run-time error a logical error no error the statement being converted to a comment

ANS: A If the Java compiler cannot make sense of a command, the compiler cannot convert it and responds with a syntax error. While println is recognized as a command, printn is not, and so the compiler provides a syntax error.

PROBLEM 1. What is wrong with the following class definition? public class Program1 { public static void main(String[ ] args) { System.out.println("My first Java program") } } ANS: The one executable statement in the main method is missing a ";" at the end of the line. Executable statements end with ";". 2. What is wrong with the following class definition? public class Program2 public static void main(String[] args) { System.out.println("My second Java program"); } ANS: The definition of a class is placed within {} statements, which are missing here. 3. Given the following class definition, what are the reserved words and what are the identifiers? public class Program3

{ public static void main(String[] args) { System.out.println("My third Java program"); } } ANS: The reserved words are public, class, static, void. The identifiers are main, String, System.out, Program3, and args. main is the name of a method defined within the Program3 class. string and System.out are classes already defined in Java and println is a method of System.out. Program3 is a class, defined here, and args is a variable. 4. Provide a brief explanation of the role of main memory, the control unit, the arithmetic logic unit, and registers. (Refer to figure 1.13 in the text) ANS: Main memory is used to store the currently executing processes along with their data. The control unit performs the fetch-decode-execute cycle, which fetches an instruction from memory, decodes it and determines how it is to be executed. The arithmetic logic unit comprises a number of circuits that execute arithmetic and logic instructions. Registers are used to store values in the CPU temporarily while the current instruction(s) need them. 5. What is the output of the following code when the main method is executed? public class Question4 { public static void main(String[] args) { System.out.println("hi there"); System.out.println(" "); System.out.println("how are you doing } }

today?

");

ANS: hi there how are

you doing

today?

Notice that while the Java compiler ignores "white space", blanks that appear in a println statement inside of quote marks are retained and output in that manner. 6. What is wrong with the following println statement? System.out.println("My fourth Java Program); ANS: It is missing a closing ". The compiler will look for a second " before the end of the statement. So, like {}, (), and [], an initial " must have a corresponding closing ". 7. Provide identifier names that would be used to represent a person's social security number, income tax withheld, and net pay.

ANS: socialSecurityNumber, or ssn, incomeTaxWithheld or incomeTax, and netPay all would be reasonable. 8. There are a number of reserved words in Java that have no current meaning (denoted with an * in figure 1.18 in the text). Why? ANS: Java language designers anticipate introducing these statements in future versions, but have not yet implemented them because they are lower priority, or it has not been decided how they will be implemented or precisely what they will mean. 9. A document of text is 15 pages long. Each page contains approximately 200 words and the average length of each word is 5 characters. Also assume one blank space between each word and no punctuation. How many bytes will it take to store this document in memory or on disk using ASCII? ANS: A character is stored in ASCII using 8 bits or 1 byte. Therefore, 5 characters per word plus 1 blank space between words take 6 bytes per word (except for the first). Each page stores 200 words and there are 15 pages. So we need 15 * 200 * 6 - 1 (no blank space to start the text) = 17,999 bytes which is 17.58 kilobytes, or nearly 18 Kbytes. 10. Provide a brief description of the roles of the following hardware elements (that is, what each is used for): a) CPU b) Main memory c) Secondary memory devices d) Input/Output devices ANS: a) The CPU is the processor. It executes all program instructions. It does this through the fetchdecode-execute cycle where the next program instruction is fetched from memory, decoded in the CPU, and then executed by one or more circuits. b) Main memory is stored on chips on the motherboard and is used for quick access to the current program for the fetch-decode-execute cycle and to store data being used by this program. c) Secondary memory devices are storage devices, used to store programs and data not currently being used. Storage devices, such as the hard disk, also are used to store things for permanence and archives. d) Input/Output devices are used to communicate with the computer. Input devices, like the keyboard, take commands and data from the user and output devices, like the monitor, display the results of the process/computation. 11. Examine figure 1.7 before answering this question. What 8-bit value comes immediately before and what 8-bit value comes immediately after 10010111? ANS: 10010110 comes immediately before 10010111 and 10010100 comes immediately after 10010111.

12. Rewrite the following comment so that is can appear over multiple lines. // This is one really enormously long comment that might run off the page ANS: We can do this in two ways, preceding each line with // or by enclosing the comment in /* and */. /* This is one really enormously long comment that might run off the page */ or // This is one really enormously // long comment that might run // off the page 13. Rewrite the following program with better formatting to make it easier to read. public class MyProgram { public static void main( String[] args) { System.out.println( "Wow, this is messed up!" ); } } ANS: There are many ways this program might appear. The following would be very acceptable: public class MyProgram { public static void main(String[] args) { System.out.println("Wow, this is messed up!"); } } 14. Write a Java program that will output on two separate lines the names of the authors of this textbook. ANS: public class OutputNames { public static void main(String[] args) { System.out.println("John Lewis"); // 1st author's name System.out.println("William Loftus");// 2nd author's name } }

15. Correct all the syntax errors in the following program. Public Class Program \\ A problem program ( Public static voided main[Strings() args] { system.out.println('This program'); \* oh, my... *\ system.out.println('has several syntax errors'); \* lots of errors *\ } ) ANS: public class Program // A problem program { public static void main(String[] args) { System.out.println("This program"); /* oh, my... */ System.out.println("has several syntax errors"); /* lots of errors */ } } 16. Write a Java program that will display the following three lines when it is run: * * * * * * * * * ANS: public class Stars { public static void main(String[] args) { System.out.println(" *"); System.out.println(" * * *"); System.out.println("* * * * *"); } }

17. Name five of the fundamental terms which encompass object-oriented programming. ANS:

There are seven terms to choose from: object, attribute, method, class, encapsulation, inheritance, and polymorphism.

9. Reserved words in Java can be redefined by the programmer to mean something other than their original intentions. ANS: F Java reserved words cannot be redefined. 10. In a Java program, dividing by zero is a syntax error. ANS: F Dividing by 0 is not detected at compile time, and because a computer cannot divide by 0, this is a run-time error. 11. In a Java program, dividing by zero is a syntax error. ANS: F Dividing by 0 is not detected at compile time, and because a computer cannot divide by 0, this is a run-time error. 12. During translation, the compiler puts its output (the compiled Java program) into ROM. ANS: F ROM stands for read-only-memory. The compiled output (the byte codes) may be placed into RAM (writable random access memory) or into a file (on your hard drive, for example). 13. Objects are defined by a class that describes the characteristics common to all instances of the class. ANS: T An object is an instance of a class. And, the purpose of a class is to describe these common characteristics.

MULTIPLE CHOICE 1. A Java program is best classified as a. b. c. d. e.

hardware software storage processor input

6 20 24 32 64

ANS: E With n bits, we can represent 2^n different values. 2^6 = 64. 3. When executing a program, the processor reads each program instruction from a. secondary memory (storage) b. the Internet

1,500,000,000,000 bytes 100 gigabytes 3,500,000 kilobytes 10 terabytes 12,000,000 megabytes

0s 1s 0s and 1s any digits between 0 and 9 0s, 1s, and 2s

ANS: C Binary is base 2. In Mathematics, numbers in base n are composed entirely of digits between 0 and n-1. 6. Volatility is a property of a. b. c. d. e.

RAM ROM disk software computer networks

ANS: A

random access sequential access read-only access fetch access

fetch decode execute during fetch or execute, but not decode any of the phases

MODEM communication line network address packet router

the TCP protocol the IP protocol the combined TCP/IP protocol the Ethernet protocol the ARPANET protocol

b. c. d. e.

computer on the Internet local area network (LAN) on the Internet a document or other type of file on the Internet a Java program on the Internet

machine language Assembly language high-level language fourth generation language both high-level and fourth generation language

public static main() public static main(String[] args); public static main(String[] args) private static main(String[] args) The main method could be defined by all of these except B

nothing cause Hello to be output cause a syntax error cause ("Hello") to be output There is no way to tell without executing the code.

ANS: A The characters // denote the beginning of a comment. The comment is not compiled and so, nothing would happen when this code is executed.

19. What comment might be added to explain the following instruction? System.out.println("Hello World"); a. b. c. d. e.

// prints "Hello World" to the screen //prints a message //used to demonstrate an output message // // meaningless instruction

$ _ 0 1 ^

System.out.println("Hi"); public class Foo s t a t i c main(String[] args) {} only A is legally valid; all the others are illegal

i class 1likeclass! idon'tlikeclass i-like-class

a. b. c. d. e.

bytecodes syntax use of objects use of exception handling All of these

Pascal Ada C++ FORTRAN BASIC

compiler error syntax error run-time error logical error snafu

curstoval theCurrentValueOfThisStock currentStockVal csv current

1ForAll oneForAll one/4/all 1_4_all 1forall

a syntax error a run-time error a logical error no error the statement being converted to a comment

today?

");

ANS: hi there how are

you doing

today?

ANS: socialSecurityNumber, or ssn, incomeTaxWithheld or incomeTax, and netPay all would be reasonable. 8. There are a number of reserved words in Java that have no current meaning (denoted with an * in figure 1.18 in the text). Why? ANS: Java language designers anticipate introducing these statements in future versions, but have not yet implemented them because they are lower priority, or it has not been decided how they will be implemented or precisely what they will mean. 9. A document of text is 15 pages long. Each page contains approximately 200 words and the average length of each word is 5 characters. Also assume one blank space between each word and no punctuation. How many bytes will it take to store this document in memory or on disk using ASCII? ANS: A character is stored in ASCII using 8 bits or 1 byte. Therefore, 5 characters per word plus 1 blank space between words take 6 bytes per word (except for the first). Each page stores 200 words and there are 15 pages. So we need 15 * 200 * 6 - 1 (no blank space to start the text) = 17,999 bytes which is 17.58 kilobytes, or nearly 18 Kbytes. 10. Provide a brief description of the roles of the following hardware elements (that is, what each is used for): a) CPU b) Main memory c) Secondary memory devices d) Input/Output devices ANS: a) The CPU is the processor. It executes all program instructions. It does this through the fetch-decode-execute cycle where the next program instruction is fetched from memory, decoded in the CPU, and then executed by one or more circuits. b) Main memory is stored on chips on the motherboard and is used for quick access to the current program for the fetch-decode-execute cycle and to store data being used by this program. c) Secondary memory devices are storage devices, used to store programs and data not currently being used. Storage devices, such as the hard disk, also are used to store things for permanence and archives. d) Input/Output devices are used to communicate with the computer. Input devices, like the keyboard, take commands and data from the user and output devices, like the monitor, display the results of the process/computation. 11. Examine figure 1.7 before answering this question. What 8-bit value comes immediately before and what 8-bit value comes immediately after 10010111? ANS: 10010110 comes immediately before 10010111 and 10010100 comes immediately after 10010111.

17. Name five of the fundamental terms which encompass object-oriented programming. ANS:

There are seven terms to choose from: object, attribute, method, class, encapsulation, inheritance, and polymorphism.

Java Software Solutions, 9e (Lewis/Loftus) Chapter 2 Data and Expressions TRUE/FALSE 1. If x is a String, then x = new String("OH"); and x = "OH"; will accomplish the same thing. ANS: T In Java, to instantiate (assign a value to) an object, you must use new and the class's constructor. However, since Strings are so common in Java, they can be instantiated in a way similar to assigning primitive types their values. So, both of the above assignment statements will accomplish the same task. 2. If x is the String "Hi There", then x.toUpperCase().toLowerCase(); will return the original value of x. ANS: F x.toUpperCase() returns x as all capital letters, while x.toLowerCase()will return x as all lower case letters. So, this code will first convert x to all upper case letters and then convert the new version to all lower case characters. 3. If String name = "George W. Bush"; then the instruction name.length(); will return 14. ANS: T There are 14 characters between the quote marks including two blanks and a period. 4. If String a = "ABCD" and String b = "abcd" then a.equals(b); returns false but a.equalsIgnoreCase(b); returns true. ANS: T Since "ABCD" is not the same as "abcd", the equals method returns false, but by ignoring case in equalsIgnoreCase, the two are considered to be the same. 5. Unlike the String class where you must pass a message to an object (instance) of the class, as in x.length(), in order to use either the Scanner or Math classes, you pass messages directly to the class name, as in Math.abs()or scan.nextInt(). ANS: T The Math and Scanner classes use methods known as static methods (or class methods) which are invoked by passing a message directly to the class name itself rather than to an object of the class. 6. In order to generate a random number, you must use Math.random().

ANS: F There is also a Random class available in java.util. This class can generate random int, float, and double values. This is a better mechanism for generating random numbers because you can instantiate several different random number generators. 7. A double is wider than a float and a float is wider than an int. ANS: T Wider types are larger in size or can store a greater range of values. The double is 64 bits whereas the float is 32 bits and the float, because of the way it is stored, can store a significantly larger range of values than the int. 8. A variable of type boolean will store either a 0 or a 1. ANS: F A boolean variable can store only one of two values, but these values are the reserved words true and false. In C, C++, and C# booleans are implemented as int variables that store only a 0 or a 1, but in Java, the authors of the language opted to use the boolean literals true and false as this is considered to be semantically more understandable (and is much safer). 9. In Java, 'a' and 'A' are considered to be different values. ANS: T Characters values are stored using ASCII, and 'a' and 'A' have different ASCII values as well as different Unicode values. 10. You cannot cast a String to be a char and you cannot cast a String which stores a number to be an int, float, or double. ANS: T There is no mechanism available to cast a String to one of the primitive types, but there are methods available to perform a similar action and return a character at a given location (CharAt) or to return the int, float, or double value equivalent to the number stored in the String. 11. The values of (double)5/2 and (double)(5/2) are identical. ANS: F In the first expression, the (double) cast applies to theint 5, changing it to the double value, 5.0. Then 5.0/2 is calculated, yielding the double value, 2.5. In the second expression the int division is performed first, yielding the value 2. 2 is then changed to a double, yielding the double value, 2.0. 12. There are three ways that data conversion may occur: by assignment, by promotion, and by casting.

ANS: T Assignment conversion occurs when a value on the right side of the assignment operator is converted prior to being stored in the variable on the left. Promotion occurs within an expression when values of differing widths are combined. Casting is a programmer's explicit way to control the data conversion process. 13. As explained in the Software Failure section in the text, the Mars Lander most likely crash landed when its descent engines cut off too high over the Mars surface. ANS: T The software on board the lander mistook the vibrations caused by the deployment of the lander's legs for the vibration caused by actually landing on the planet's surface.

MULTIPLE CHOICE Example Code Ch 02-1 public class Questions1_4 { public static void main(String[] args) { System.out.print("Here"); System.out.println("There " + "Everywhere"); System.out.println("But not" + "in Texas"); } } 1. Refer to the class definition in Example Code Ch 02-1. The program will print the word "Here" and then print a. b. c. d. e.

"There Everywhere" on the line after "Here" "The" on the line after "Here" and "Everywhere" on the line after "There" "There Everywhere" on the same line as "Here" "ThereEverywhere" on the same line as "Here" "ThereEverywhere" on the line after "Here"

ANS: C System.out.print will output the word Here but will leave the cursor at that point rather than starting a new line. The next statement will output There Everywhere immediately after the word Here. Since there is a blank space within the quote marks for There, there is a blank space inserted between There and Everywhere. 2. Refer to the class definition in Example Code Ch 02-1. The final println command will output a. b. c. d. e.

"But not in Texas" "But notin Texas" "But not" on one line and "in Texas" on the next line "But not+in Texas" "But not + in Texas"

ANS: B

The + performs String concatenation, so that But not and in Texas are concatenated together. Notice that there is no blank space after not or before in so that when they are concatenated, they are placed together without a blank space. 3. Refer to the class definition in Example Code Ch 02-1. How many lines of output are provided by this program? a. b. c. d. e.

1 2 3 4 5

ANS: B There will be one line of output for the first two statements combined because the print statement does not return the cursor to start a new line. And since the second statement is a println, it returns the cursor and the last println outputs its message on a separate line. 4. Refer to the class definition in Example Code Ch 02-1. A reasonable documentation comment for this program might be a. //a program that demonstrates the differences between print, println, and how + works b. //a program that outputs a message about Texas c. //a program that demonstrates nothing at all d. //a program that outputs the message "Here There Everywhere But not in Texas e. //a program that contains three output statements ANS: A Remember that comments should not state the obvious (ruling out D and E) but instead should explain what the program is doing or why. This program demonstrates print and println and +. 5. The following statement will output __________ lines of text. System.out.println("1 big bad wolf\t8 the 3 little pigs\n4 dinner\r2night"); a. b. c. d. e.

1 2 3 4 5

ANS: B The \t escape sequence inserts a tab, but leaves the cursor on the same line. The \n escape sequence causes a new line to be produced so that 4 dinner is output on the next line. The escape sequence \r causes the carriage to return (that is, the cursor to be moved back to the left margin) but because it does not start a new line, 2night is output over 4 dinn resulting in a second line that looks like 2nighter. 6. If you want to output the text "hi there" including the quote marks, which of the following would you use?

a. b. c. d. e.

System.out.println("hi there"); System.out.println(""hi there""); System.out.println("\"hi there"); System.out.println("\"hi there\""); None of these; it is not possible to output a quote mark because it is used to mark the beginning and end of the String to be displayed.

ANS: D \" is an escape sequence used to place a quote mark in a String, so it is used here to output the quote marks with the rest of the String. 7. The word println is a(n) a. b. c. d. e.

method reserved word variable class String

ANS: A The word println is passed as a message to the System.out object, and so println is a method. 8. A Java variable is the name of a a. numeric data value stored in memory b. data value stored in memory that cannot change during the program's execution c. data value stored in memory that can change its value but cannot change its type during the program's execution d. data value stored in memory that can change both its value and its type during the program's execution e. data value or a class stored in memory that can change both its value and its type during the program's execution ANS: C A variable can change its value as long as it is within the same type, but the variable cannot change type. A constant is similar to a variable but it cannot change its value. Variables can be numeric but are not restricted to being numeric, they can also be boolean, char, or an object of any class. 9. Of the following types, which one cannot store a numeric value? a. b. c. d. e.

int double float char All of these can store numeric values

ANS: D int and byte are used to store whole numbers (integers) and float is used to store a real or floating point value (value with a decimal point). A char stores a single character including letters, punctuation marks and digits. However, storing the numeric digit '5' is not the same as storing the number 5.

10. What is the value of z after the following assignment statement is executed? float z = 5/10; a. b. c. d. e.

0.0 0.5 5.0 0.05 None of these; a run-time error will occur because z is a float and 5/10 is an int.

ANS: A 5 and 10 are both int values, so 5 / 10 is an integer division. The result is 0. Even though z is a float and can store the real answer, 0.5, it only gets 0 because of the integer division. In order to get 0.5, we would have to first cast 5 or 10 as a float. 11. Which of the following situations would require a cast? a. b. c. d. e.

using charAt to take an element of a String and store it in a char storing an int in a float storing a float in a double storing a float in an int All of these require casts

ANS: D For A, charAt returns a char, so there is no problem. In B and C, the situations are widening operations taking a narrower type and storing the value in a wider type. Only in D is there a situation where a wider type is being stored in a narrower type, so a cast is required. 12. If x is an int and y is a float, which of the following statements is not a legal assignment statement? a. b. c. d. e.

y = x; x = y; y = (float)x; x = (int)y; All of these are legal assignment statements

ANS: B Since x is an int, it cannot except a float unless the float is cast as an int. There is no explicit cast in the assignment statement in B. In A, a cast is not necessary because a float (y) can accept an int value (x), and in C and D, explicit casts are present making them legal. 13. What will be the result of the following assignment statement, given that b = 5 and c = 10? int a = b * (-c + 2)/2; a. b. c. d. e.

30 -30 20 -20 -6

ANS: D The unary minus is applied first giving -c + 2 = -8. Next, the * is performed giving 5*-8=40, and finally the / is performed giving -40/2 = -20.

14. Which of the following is true regarding the mod operator, %? a. b. c. d. e.

It can only be performed on int values and its result is a double. It can only be performed on int values and its result is an int. It can only be performed on float or double.values and its result is an int. It can only be performed on float or double.values and its result is a double. It can be performed on any numeric values and its result is always numeric.

ANS: E Mod, or modulo, returns the remainder that results from a division. The remainder is always is numeric. Although usually integer values are used, the % operator may be used on all kinds of numeric data. 15. Assume that x, y, and z are all ints equal to 50, 20, and 6 respectively. What is the result of: x / y / z a. b. c. d. e.

0 12 16 this would cause a syntax error this would cause a run-time error because it is a division by zero

ANS: A This division is performed left to right, so first 50/20 is performed. Since 50 and 20 are ints, this results in 2. Next, 2/6 is performed which is 0. Notice that if the division were performed right to left, the evaluation would instead be 50/(20/6) = 50/3 = 16. 16. Assume that x and y are ints equal to 10 and 5 respectively. What is the output of the following statement? System.out.println(x + y); a. b. c. d. e.

15 105 10 5 x + y this would cause an error since neither x nor y is a String

ANS: A Java first computes x+y and then casts it as a String to be output. x+y= 10 + 5 = 15, so the statement outputs 15. 17. Assume that x and y are ints equal to 10 and 5 respectively. What is the output of the following statement? System.out.println("" + x + y); a. b. c. d. e.

15 105 10 5 x + y this would cause an error since neither x nor y is a String

ANS: B The "" causes the rest of the expression to be treated as a String, and so the two + signs are used as String concatenation. Therefore x+y becomes x concatenated with y, or 105. 18. If you want to store the value "Harry Potter" in the String variable name, which of the following statements could you use? a. b. c. d. e.

String name = "Harry Potter"; String name = new String("Harry Potter"); String name = "Harry" + " " + "Potter"; String name = new String("Harry" + " " + "Potter"); Any of these would work

ANS: E There are two ways to store a character string into a String variable, by constructing a new String using new String(string value); or by using an assignment statement, so either A or B will work. In C and D, we have variations where the String concatenation operator is used. So all four approaches will work. 19. Given three String variables, a, b, and c, which of the following statements could you use to achieve the same thing as: c = a + b; a. b. c. d. e.

c = a.length() + b.length(); c = (int)a + (int)b; c = a.concat(b); c = b.concat(a); c = a.plus(b);

ANS: C The statement c = a + b uses the concatenation operator (not to be confused with numeric addition). The same result can be achieved by passing a the concat message with b as the parameter. Answer D will set c to be b + a rather than a + b. 20. If the String major = "Computer Science", what is returned by major.charAt(1)? a. b. c. d. e.

'C' 'o' 'm' "C" "Computer"

ANS: B Neither D nor E would be correct because charAt returns a char (single character) whereas these answers are Strings. So, the question is, which character is returned? In Java, the first character of a String is numbered 0. So charAt(1) returns the second character of the String, or 'o'. 21. Which of the following would return the last character of the String x? a. x.charAt(0); b. x.charAt(last); c. x.charAt(length(x));

d. x.charAt(x.length()-1); e. x.charAt(x.length()); ANS: D Since last is not defined, B is syntactically invalid. The 0th character is the first in the String, so A is true only if the String has a single character. The answer in C is syntactically invalid as length can only be called by passing the message to x. Finally, D and E are syntactically valid, but since length returns the size of the String, and since the first character starts at the 0th position, the last character is at x.length()-1, so E would result in a run-time error. 22. Given String name = "Arleen Crabtree". What will the following instruction return? name.toUpperCase().replace('R', 'Z'); a. b. c. d. e.

"ARLEEN CRABTREE" "AZLEEN CZABTREE" "Azleen Czabtree" "Arleen Crabtree" "ArZleen CrZabtree"

ANS: B The toUpperCase method returns the String as all upper case characters, or "ARLEEN CRABTREE". The replace method will replace each instance of R with Z. 23. Which library package would you import to use NumberFormat and DecimalFormat? a. b. c. d. e.

java.beans java.io java.lang java.text java.util

ANS: D Both of these classes are used for "text processing", that is, to handle values like Strings. Such classes are found in java.text. You might think these would be in java.io, but this library has classes related to input and sending output to locations other than the monitor. 24. Which library package would you import to use the class Random? a. b. c. d. e.

java.beans java.io java.lang java.text java.util

ANS: E This is a Java numeric utility, and so is found in the java.util package. 25. The Random class has a method, nextFloat() which returns a random float value between a. b. c. d.

-1 and +1 0 and 1 0 and 99 1 and 100

e. -2,147,483,648 and +2,147,483,647 ANS: B The method nextFloat() returns a float value between 0 and 1 so that it may be used as a probability. 26. If you want to output a double so that at least one digit appears to the left side of the decimal point and exactly one digit appears to the right side, which pattern would you give a DecimalFormat variable when you instantiate it? a. b. c. d. e.

"0.0" "0.#" "0.0#" "0.##" "#.#"

ANS: A The pattern "0.0" says to output all of the digits to the left of the decimal point or a 0 if there are none (you want at least 1 digit to the left, including a 0 if there are no digits) and exactly one digit to the right of the decimal point, even if the digit is 0. The patterns "0.#" and "#.#" would not output any digits to the right side of the decimal point if the value had no decimal portion (e.g., 39.0). The patterns in C and D can output up to 2 values to the right of the decimal point. 27. Given the double likelihood = 0.013885 and given DecimalFormat dformatter = DecimalFormat("0.00##"); What would be the output if you execute the following: System.out.println(df.format(likelihood)); a. b. c. d. e.

0.013885 0.0139 0.0145 .0138 .014

ANS: B The format "0.00##" means that at least 1 digit should appear to the left of the decimal point, even if it is 0, that at least two digits should appear to the right of the decimal point even if they are zeros, and if there are two additional digits to the right, they should also be printed, rounding the value off as needed. So, this gives 0.0139 since the number, 0.013885 will be rounded up to 0.0139. 28. Using getCurrencyInstance() formats a variable, automatically inserting a. b. c. d. e.

a decimal point for cents a dollar sign a percent sign all three of these a decimal point for cents and a dollar sign but not a percent sign

ANS: E getCurrencyInstance will format a double or float variable so that it has 2 digits to the right of the decimal point and a dollar sign preceding the value. getPercentInstance is used to format a double or float to be output with a percent sign.

29. What will be the value of z after the following statement is executed? int z = 50 /10.00; a. b. c. d. e.

5 5.0 50 10 None of thse; a run-time error will occur because z is an int and 50/10.00 is not

ANS: E Because 10.00 is not an int, the division produces a double precision value which cannot be stored in the int z. For this to work, the result of the division must be cast as an int before being stored in z, or the value 10.00 would have to first be cast as an int before the division takes place. 30. Since you cannot take the square root of a negative number, which of the following could you use to find the square root of the variable x? a. b. c. d. e.

Math.sqrt(x*x); Math.sqrt((int)x); Math.sqrt(Math.abs(x)); Math.abs(Math.sqrt(x)); Math.sqrt(-x);

ANS: C Math.abs returns the absolute value of x. If x is negative, Math.sqrt(x)causes a run-time error, but Math.sqrt(Math.abs(x))does not since x is first converted to its positive equivalent before the square root is performed. Answer A returns x (square root of x^2 is x). In answer B, casting x to an int will not resolve the problem if x is negative. In answer D, the two Math functions are performed in opposite order and so if x is negative, it still generates a run-time error. Answer E only will work if x is not positive and so if x is positive, it now generates a run-time error. 31. Given x is a double and has the value 0.362491. To output this value as 36%, you could use the NumberFormat class with: NumberFormat nf = NumberFormat.getPercentInstance(); Which of the following statements then would output x as 36%? a. b. c. d. e.

System.out.println(x); System.out.println(nf); System.out.println(nf.format(x)); System.out.println(nf.x); System.out.println(format(x));

ANS: C nf is an object and so must be passed a message to use it. The method to format a float or double is called format and the value to be formatted is the parameter passed to format. Therefore, the proper way to do this is nf.format(x). The answer in A merely outputs 0.362491 while the answers to B, C, and E are syntactically invalid. Example Code Ch 02-2 import java.util.Scanner;

public class Questions33_34 { public static void main(String[] args) { int x, y, z; double average; Scanner scan = new Scanner(System.in); System.out.println("Enter an integer value"); x = scan.nextInt(); System.out.println("Enter another integer value"); y = scan.nextInt(); System.out.println("Enter a third integer value"); z = scan.nextInt(); average = (x + y + z) / 3; System.out.println("The result of my calculation is " + average); } } 32. Refer to Example Code Ch 02-2. This code computes a. b. c. d. e.

The correct average of x, y, and z as a double The correct average of x, y, and z as an int The average of x, y, and z as a double but the result may not be accurate The sum of x, y, and z as an int The remainder of the sum of x, y, and z divided by 3

ANS: C Because the division is an int division, even though the result is stored in a double, the resulting double may not be accurate. For instance, if x, y and z are 1, 2, and 4, the double average should be 2.33333 but average will instead be 2.00000. 33. Refer to Example Code Ch 02-2. What is the output if x = 0, y = 1, and z = 1? a. b. c. d. e.

0 0.0 0.6666666666666666 0.6666666666666667 0.67

ANS: B The division is performed as an int division since x, y, z, and 3 are all ints. Therefore, average gets the value 0.0. It is output as 0.0 instead of 0 because average is a double, which outputs at least one decimal digit unless specified otherwise using the DecimalFormat class. 34. In order to create a constant, which of the following Java reserved words is used? a. b. c. d. e.

private static int final class

ANS: D

The reserved word final indicates that this is the final value that will be stored in this variable, thus making it unchangeable, or constant. While constants can be of type int, constants can be of any other type as well. It is the final reserved word that makes the value unchangeable. 35. Given three int variables with the values a = 5, b = 7, and c = 12, what is the value of z after the following statement is executed? int z = (a * b - c) / a; a. b. c. d. e.

0 4 5 -5 23

ANS: B (a * b - c) / a = (5 * 7 - 12) / 5 = (35 - 12) / 5 = 23 / 5, and since 23 and 5 are int values, the division is performed as an int division, or 23 / 5 = 4. 36. Java is a strongly typed language. What is meant by "strongly typed"? a. Every variable must have an associated type before it can be used. b. Variables can be used without declaring their types. c. Every variable has a single type associated with it throughout its existence in the program and the variable can only store values of that type. d. Variables are allowed to change type during their existence in a program so long as the value a variable currently stores is of the type it currently declared to be. e. Variables are allowed to change types during their existence in a program but only if the change is to a narrower type. ANS: C Strong typing is a property of a programming language whereby the variable's type does not change during the variable's existence, and any value stored in that variable is of that type. The reason that strong typing is important is it guarantees that a program that was successfully compiled will not have run-time errors associated with the misuse of types for the variables declared. 37. As presented in the Software Failure section of the text, the root cause of the Mars Climate Orbiter problem was a. b. c. d. e.

the cost of the project an inability to track the orbiter at long distances atmospheric friction a communication issue between subsystems None of these

ANS: D The cause was determined to be an embarrassing communication issue between subsystems. The navigation subsystem used imperial units of measure (pound-force) and the spacecraft's software itself expected data in metric units (newtons).

PROBLEM

1. Write a set of instructions to prompt the user for an int value and input it using the Scanner class into the variable x and prompt the user for a float value and input it using the Scanner class into the variable y. ANS: Scanner scan = Scanner.create(System.in); System.out.println("Enter an integer"); int x = scan.nextInt(); System.out.println("Enter a float"); float y = scan.nextFloat(); 2. Provide an example of how you might use a boolean, a float, a char, a String, and an

int. ANS: Answers may vary. Samples: boolean to store whether a person is of voting age or not float: to store someone's GPA char: to store someone's middle initial String: to store someone's social security number int: to store someone's age 3. Explain what the following statement computes: int z = (int)Math.ceil(Math.sqrt(x)/Math.sqrt(y)); ANS: The integer value which bounds sqrt(x)/sqrt(y)where bounds means it is equal to the result of the division or the next int larger than the result of the division if the result has a remainder. 4. Given four int values, x1, x2, y1, y2, write the code to compute the distance between the two points (x1, y1) and (x2, y2), storing the result in the double distance. ANS: double distance = Math.sqrt(Math.pow(x1 - y1, 2) + Math.pow(x2 y2,2)); 5. Write an assignment statement to compute the gas mileage of a car where the int values milesTraveled and gallonsNeeded have already been input. The variable gasMileage needs to be declared and should be a double. ANS: double gasMileage = (double)milesTraveled/gallonsNeeded; The reason that the value milesTraveled is cast as a double is to ensure that the division is performed as a double and not an int.

6. Write the paint method for an applet so that it contains 4 concentric circles (each circle is inside the previous circle), where the largest circle is bounded by a 400x400 box and the smallest is bounded by a 100x100 box. Each circle is centered on an applet that is 400x400. Make each circle a different color of your choice. ANS: public void paint(Graphics page) { page.setColor(Color.white); page.fillOval(0, 0, 400, 400); page.setColor(Color.yellow); page.fillOval(50, 50, 300, 300); page.setColor(Color.orange); page.fillOval(100, 100, 200, 200); page.setColor(Color.red); page.fillOval(150, 150, 100, 100); } 7. Given two points in an applet represented by the four int variables x1, y1, x2 and y2, write a paint method to draw a line between the two points and write the location of the two points next to the two points. ANS: public void paint(Graphics page) { page.setColor(Color.blue); page.drawLine(x1, y1, x2, y2); page.drawString("" + x1 + ", " + y1, x1, y1); page.drawString("" + x2 + ", " + y2, x2, y2); } 8. An employer has decided to award a weekly pay raise to all employees by taking the square root of the difference between his weight and the employee's weight. For instance, an employee who weighs 16 pounds less than the employer will get a $4 per week raise. The raise should be in whole dollars (an int). Assume that employerWeight and employeeWeight are both int variables that have been input. Write an assignment statement to compute the int value for raise. ANS: raise = (int) Math.sqrt(Math.abs(employerWeight - employeeWeight)); The absolute value of the difference must be taken in case the employee weighs more than the employer, which would then result in an attempt to take the square root of a negative number. So Math.abs is used. After computing the absolute value of the difference, the square root is taken and the result (a double) is cast as an int to be stored in raise. 9. Using the various String methods, manipulate a String called current to be the last character of current followed by the remainder of its characters in order, placing the result in a String called rearranged. ANS:

String rearranged = current.charAt(current.length() - 1) + current.substring(0, current.length() - 2); The last character, which is found at charAt(current.length() - 1) is the first item in rearranged, followed by the substring of current starting at 0 (the first character) and going to current.length() - 2 (the second to last character). 10. How many ways are there to test to see if two String variables, a and b, are equal to each other if we ignore their case (for instance, "aBCd" would be considered equal to "ABcd")? ANS: There are at least 10 ways that this can be done: a.toLowerCase().equals(b.toLowerCase()); b.toLowerCase().equals(a.toLowerCase()); a.toUpperCase().equals(b.toUpperCase()); b.toUpperCase().equals(a.toUpperCase()); a.equalsIgnoreCase(b); b.equalsIgnoreCase(a); a.equalsIgnoreCase(b.toLowerCase()); a.equalsIgnoreCase(b.toUpperCase()); b.equalsIgnoreCase(a.toLowerCase()); b.equalsIgnoreCase(a.toUpperCase()); 11. How do the statements "import java.util.*;" and "import java.util.Random;"

differ from each other? ANS: In the former, all of the classes defined in the java.util library are imported whereas in the latter, only the Random class is imported from the java.util library. The former approach is easier but more time consuming and wasteful of memory, so the latter approach is more appropriate if you only want to use a single class from a given library. 12. Assume that a = "1", b = "2", y = 3, and z = 4. How do the following two statements differ? System.out.println(a + b + y + z); System.out.println(y + z + a + b); ANS: In the first statement, since a and b are Strings, a + b + c + d is treated as String concatenation and the statement outputs 1234. In the second statement, y + z is treated as int addition, which is then cast as a String to be concatenated with y + z, giving 712 instead of 3412 as you might expect. 13. Write a program which will input an int value, x, and compute and output the values of 2^x and x^10 as int values. ANS: import java.util.Scanner;

public class Compute14 { public static void main(String[] args) { Scanner scan = Scanner.create(System.in); System.out.println("Enter an integer value"); int x = scan.nextInt(); int twoToTheX = (int) Math.pow(2, x); int xToThe10th = (int) Math.pow(x, 10); System.out.println("The results are " + twoToTheX + " and " + xToThe10th); } } 14. What is wrong with the following assignment statement? Assume x and y are both String objects. String z = x.equals(y); ANS: The equals method returns a boolean value, not a String. The values true and false are not the same as the values "true" and "false. 15. Write a program that will input some number of cents (less than 100) and output the number of quarters, dimes, nickels and pennies needed to add up to that amount. ANS: import java.util.Scanner; public class Change { public static void main(String[] args) { Scanner scan = Scanner.create(System.in); System.out.println("Enter the amount of change"); int amount = scan.nextInt(); System.out.println("The change for " + amount " cents is: "); int quarters = amount / 25; System.out.println(" " + quarters + " quarters"); amount = amount - quarters * 25; int dimes = amount / 10; System.out.println(" " + dimes + " dimes"); amount = amount - dimes * 10; int nickels = amount / 5; System.out.println(" " + nickels + " nickels"); amount = amount - nickels * 5; int pennies = amount; System.out.println(" " + pennies + " pennies"); } } 16. Write an output statement which will output the following characters exactly as shown: / ' \" / ' \

ANS: System.out.println("/ \ ' \ \ \" / \ ' \ \ ");

17. Provide three examples of code using assignment statements where one assignment statement would result in a syntax error, one would result in a logical error, and one would result in a run-time error. ANS: Answers will vary. Examples: // syntax error caused by right side providing a double and the left side wants an int: int x = 5.0 / 2.0; // logical error caused by not casting the division as a double: double x = (intValue1 + intValue2) / 2; // run-time error caused by division by 0 when y - y is evaluated: int x = 5 / (y - y); 18. What are the syntax errors from the following program? public class Enigma { public static void main(String[] args) { System.out.println("Input a String"); String x = scan.nextString(); int size = x.length; char last = x.charAt(size); System.out.println("The last character in your string ", x, " is ", last); } } ANS: There are 3 syntax errors. First, the Scanner class has not been imported so that the scan.nextString()will yield a syntax error. Second, the statement x.length requires parentheses as length is a method of the class String, so this is a message passed to x. Finally, the System.out.println statement is not valid because of the use of a comma instead of + to concatenate the various parts of the String. Note that in spite of these syntax errors, there is a runtime error. This error would arise because size will store the length of the String, but the last character will be at location size-1 instead of size. Thus, the statement char last = x.charAt(size); will result in a run-time error because size is beyond the bounds of the String x.

There is also a Random class available in java.util. This class can generate random int, float, and double values. This is a better mechanism for generating random numbers because you can instantiate several different random number generators. 7. A double is wider than a float and a float is wider than an int. ANS: T Wider types are larger in size or can store a greater range of values. The double is 64 bits whereas the float is 32 bits and the float, because of the way it is stored, can store a significantly larger range of values than the int. 8. A variable of type boolean will store either a 0 or a 1. ANS: F A boolean variable can store only one of two values, but these values are the reserved words true and false. In C, C++, and C# booleans are implemented as int variables that store only a 0 or a 1, but in Java, the authors of the language opted to use the boolean literals true and false as this is considered to be semantically more understandable (and is much safer). 9. In Java, 'a' and 'A' are considered to be different values. ANS: T Characters values are stored using ASCII, and 'a' and 'A' have different ASCII values as well as different Unicode values. 10. You cannot cast a String to be a char and you cannot cast a String which stores a number to be an int, float, or double. ANS: T There is no mechanism available to cast a String to one of the primitive types, but there are methods available to perform a similar action and return a character at a given location (CharAt) or to return the int, float, or double value equivalent to the number stored in the String. 11. The values of (double)5/2 and (double)(5/2) are identical. ANS: F In the first expression, the (double) cast applies to theint 5, changing it to the double value, 5.0. Then 5.0/2 is calculated, yielding the double value, 2.5. In the second expression the int division is performed first, yielding the value 2. 2 is then changed to a double, yielding the double value, 2.0. 12. There are three ways that data conversion may occur: by assignment, by promotion, and by casting. ANS: T

Assignment conversion occurs when a value on the right side of the assignment operator is converted prior to being stored in the variable on the left. Promotion occurs within an expression when values of differing widths are combined. Casting is a programmer's explicit way to control the data conversion process. 13. As explained in the Software Failure section in the text, the Mars Lander most likely crash landed when its descent engines cut off too high over the Mars surface. ANS: T The software on board the lander mistook the vibrations caused by the deployment of the lander's legs for the vibration caused by actually landing on the planet's surface.

"But not in Texas" "But notin Texas" "But not" on one line and "in Texas" on the next line "But not+in Texas" "But not + in Texas"

ANS: B

1 2 3 4 5

a. b. c. d. e.

ANS: D \" is an escape sequence used to place a quote mark in a String, so it is used here to output the quote marks with the rest of the String. 7. The word println is a(n) a. b. c. d. e.

method reserved word variable class String

int double float char All of these can store numeric values

10. What is the value of z after the following assignment statement is executed? float z = 5/10; a. b. c. d. e.

0.0 0.5 5.0 0.05 None of these; a run-time error will occur because z is a float and 5/10 is an int.

using charAt to take an element of a String and store it in a char storing an int in a float storing a float in a double storing a float in an int All of these require casts

y = x; x = y; y = (float)x; x = (int)y; All of these are legal assignment statements

30 -30 20 -20 -6

ANS: D The unary minus is applied first giving -c + 2 = -8. Next, the * is performed giving 5*-8=-40, and finally the / is performed giving -40/2 = -20.

14. Which of the following is true regarding the mod operator, %? a. b. c. d. e.

0 12 16 this would cause a syntax error this would cause a run-time error because it is a division by zero

15 105 10 5 x + y this would cause an error since neither x nor y is a String

String name = "Harry Potter"; String name = new String("Harry Potter"); String name = "Harry" + " " + "Potter"; String name = new String("Harry" + " " + "Potter"); Any of these would work

c = a.length() + b.length(); c = (int)a + (int)b; c = a.concat(b); c = b.concat(a); c = a.plus(b);

'C' 'o' 'm' "C" "Computer"

"ARLEEN CRABTREE" "AZLEEN CZABTREE" "Azleen Czabtree" "Arleen Crabtree" "ArZleen CrZabtree"

java.beans java.io java.lang java.text java.util

ANS: E This is a Java numeric utility, and so is found in the java.util package. 25. The Random class has a method, nextFloat() which returns a random float value between a. b. c. d.

-1 and +1 0 and 1 0 and 99 1 and 100

"0.0" "0.#" "0.0#" "0.##" "#.#"

0.013885 0.0139 0.0145 .0138 .014

a decimal point for cents a dollar sign a percent sign all three of these a decimal point for cents and a dollar sign but not a percent sign

29. What will be the value of z after the following statement is executed? int z = 50 /10.00; a. b. c. d. e.

5 5.0 50 10 None of thse; a run-time error will occur because z is an int and 50/10.00 is not

Math.sqrt(x*x); Math.sqrt((int)x); Math.sqrt(Math.abs(x)); Math.abs(Math.sqrt(x)); Math.sqrt(-x);

System.out.println(x); System.out.println(nf); System.out.println(nf.format(x)); System.out.println(nf.x); System.out.println(format(x));

0 0.0 0.6666666666666666 0.6666666666666667 0.67

private static int final class

ANS: D

0 4 5 -5 23

the cost of the project an inability to track the orbiter at long distances atmospheric friction a communication issue between subsystems None of these

PROBLEM

int. ANS: Answers may vary. Samples: boolean to store whether a person is of voting age or not float: to store someone's GPA char: to store someone's middle initial String: to store someone's social security number int: to store someone's age 3. Explain what the following statement computes: int z = (int)Math.ceil(Math.sqrt(x)/Math.sqrt(y)); ANS: The integer value which bounds sqrt(x)/sqrt(y)where bounds means it is equal to the result of the division or the next int larger than the result of the division if the result has a remainder. 4. Given four int values, x1, x2, y1, y2, write the code to compute the distance between the two points (x1, y1) and (x2, y2), storing the result in the double distance. ANS: double distance = Math.sqrt(Math.pow(x1 - y1, 2) + Math.pow(x2 - y2,2)); 5. Write an assignment statement to compute the gas mileage of a car where the int values milesTraveled and gallonsNeeded have already been input. The variable gasMileage needs to be declared and should be a double. ANS: double gasMileage = (double)milesTraveled/gallonsNeeded; The reason that the value milesTraveled is cast as a double is to ensure that the division is performed as a double and not an int.

{ public static void main(String[] args) { Scanner scan = Scanner.create(System.in); System.out.println("Enter an integer value"); int x = scan.nextInt(); int twoToTheX = (int) Math.pow(2, x); int xToThe10th = (int) Math.pow(x, 10); System.out.println("The results are " + twoToTheX + " and " + xToThe10th); } } 14. What is wrong with the following assignment statement? Assume x and y are both String objects. String z = x.equals(y); ANS: The equals method returns a boolean value, not a String. The values true and false are not the same as the values "true" and "false. 15. Write a program that will input some number of cents (less than 100) and output the number of quarters, dimes, nickels and pennies needed to add up to that amount. ANS: import java.util.Scanner; public class Change { public static void main(String[] args) { Scanner scan = Scanner.create(System.in); System.out.println("Enter the amount of change"); int amount = scan.nextInt(); System.out.println("The change for " + amount " cents is: "); int quarters = amount / 25; System.out.println(" " + quarters + " quarters"); amount = amount - quarters * 25; int dimes = amount / 10; System.out.println(" " + dimes + " dimes"); amount = amount - dimes * 10; int nickels = amount / 5; System.out.println(" " + nickels + " nickels"); amount = amount - nickels * 5; int pennies = amount; System.out.println(" " + pennies + " pennies"); } } 16. Write an output statement which will output the following characters exactly as shown: / ' \" / ' \ ANS:

System.out.println("/ \ ' \ \ \" / \ ' \ \ ");

17. Provide three examples of code using assignment statements where one assignment statement would result in a syntax error, one would result in a logical error, and one would result in a run-time error. ANS: Answers will vary. Examples: // syntax error caused by right side providing a double and the left side wants an int: int x = 5.0 / 2.0; // logical error caused by not casting the division as a double: double x = (intValue1 + intValue2) / 2; // run-time error caused by division by 0 when y - y is evaluated: int x = 5 / (y - y); 18. What are the syntax errors from the following program? public class Enigma { public static void main(String[] args) { System.out.println("Input a String"); String x = scan.nextString(); int size = x.length; char last = x.charAt(size); System.out.println("The last character in your string ", x, " is ", last); } } ANS: There are 3 syntax errors. First, the Scanner class has not been imported so that the scan.nextString()will yield a syntax error. Second, the statement x.length requires parentheses as length is a method of the class String, so this is a message passed to x. Finally, the System.out.println statement is not valid because of the use of a comma instead of + to concatenate the various parts of the String. Note that in spite of these syntax errors, there is a run-time error. This error would arise because size will store the length of the String, but the last character will be at location size-1 instead of size. Thus, the statement char last = x.charAt(size); will result in a run-time error because size is beyond the bounds of the String x.

Java Software Solutions, 9e (Lewis/Loftus) Chapter 3 Using Classes and Objects TRUE/FALSE 1. Only difficult programming problems require a pseudocode solution before the programmer creates the program itself. ANS: F Some form of design should be created for all problems before the program is written, with the possible exception of only the most trivial of problems. The form of the design may vary. For instance, programmers in the 1960s and 1970s often used flowcharts instead of pseudocode. 2. You may apply the prefix and postfix increment and decrement operators to instances of the Integer class. ANS: F These operators may only be applied to numeric data. An instance of a class is an object and and not a piece of primitive data. 3. In Java, the symbol "=" and the symbol "==" are used interchangeably. ANS: F "=" is used for assignment statements while "==" is used to test equality in conditional statements. 4. When comparing any primitive type of variable, the == operator should always be used to test if two values are equal. ANS: F This is true of int, short, byte, long, char and boolean, but not of double or float variables. If two double variables, x and y, are being tested, (x == y) is true only if they are exactly equal to the last decimal point. It is common instead to compare these two values but allow for a small difference in value. For instance, if THETA = 0.000001, we might test x and y by (x - y <= THETA) instead of (x == y) to get a better idea of whether they are close enough to be considered equal. 5. These two ways to set up a String will yield identical results: String my_string = "12345"; String my_string = 12345; ANS: F In fact, the second statement won't even compile! The second statement will receive a syntax error about incompatible types. There is no automatic conversion from a number to a String. 6. These two ways to set up a String will yield identical results: String my_string = new String("a bunch of words");

String my_string = "a bunch of words"; ANS: T Java has a very strong notion about what Strings are and how they function. The second declaration is merely shorthand for the first. The string reference will be initialized identically by both declarations. 7. These two ways to set up a String will yield identical results: String my_string = new String("123.45"); String my_string = "" + 123.45; ANS: T Java understands the + operator when used to combine Strings with numbers means that the number should be converted into a numeric String, and then concatenation should occur. 8. These two ways to set up a String will yield identical results: String my_string = new String(12345); String my_string = new String("12345"); ANS: F In fact, the first statement won't even compile! There is no overloaded version of the String constructor that accepts a numeric argument. 9. The following statement will display the value 127. System.out.println("123" + 4); ANS: F "123" is a String. So, the + will cause String concatenation to occur. The int 4 will be converted into the String "4", and the String "1234" will be created and displayed. 10. You may use the String.replace() method to remove characters from a String. ANS: F The replace() method only replaces single characters with other single characters. The replace() method will not add or delete characters to a String; the String length will remain the same. 11. If you need to import not only the top-level of a package, but all its secondary levels as well, you should use the following: import package.*.*; ANS: F The import statement can only be used with a single * (wild card). If you need to import all the secondary levels of a package as well, you must write them out explicitly: import package.A.*; import package.B.*;

12. All the methods in the Math class are declared to be static. ANS: T The Math class methods are designed to be generally useful in arithmetic expressions, so no instances of anything are required to make use of them. This is achieved by ensuring that all the Math methods are static. 13. The printf method within System.out is designed to ease the conversion of legacy C code into Java. ANS: T

C programs use the C printf function for output. Java's printf method is modeled closely after the C printf function, so C output statements can be translated into Java extremely easily. 14. The names of the wrapper classes are just the names of the primitive data types, but with an initial uppercase letter. ANS: F This is true for most of the wrapper classes, but it is false for int (Integer) and char (Character).

MULTIPLE CHOICE 1. In Java a variable may contain a. b. c. d. e.

a value or a reference a package a method a class Any of these

ANS: A Java variables contain values or references to instances of classes (which contain values and/or additional references). 2. If two variables contain aliases of the same object then a. b. c. d. e.

the object may be modified using either alias the object cannot be modified unless there's a single reference to it a third alias is created if/when the object is modified the object will become an "orphan" if both variables are set to null answers A and D are both correct

ANS: E By definition, an alias provides a means by which an object can be modified (an alias is like a pointer). If both variables are set to null, then the object is not referenced by any variable (via any alias) and it does, indeed, become an "orphan" and it will be garbage collected at some point in the future.

3. Which properties are true of String objects? a. b. c. d. e.

Their lengths never change. The shortest String has zero length. Individual characters within a String may be changed using the replace method. The index of the first character in a String is one. Only answers A and B are true.

ANS: E Strings are immutable. That means that once a String object is created it cannot be changed. Therefore the length of a String never changes once it has been created. The shortest length String is "". Since there are no characters between the quotes, the length is zero. The replace method allows you to create a new String from an original one, replacing some of the characters. The index of the first location in a String is zero, not one. Also, the last byte of every String contains the end-of-string character which is a byte of low-values, or binary zeros.

4. What happens if you attempt to use a variable before it has been initialized? a. b. c. d. e.

A syntax error may be generated by the compiler. A run-time error may occur during execution. A "garbage" or "uninitialized" value will be used in the computation. A value of zero is used. Only answers A and B are correct.

ANS: E Many times the compiler is able to detect the attempted use of an uninitialized variable and it will generate a syntax error in this case. If such a use escapes detection by the compiler then a run-time error occurs upon usage. Java is a very "safe" language, so it does not allow "garbage" or zero to be used if an uninitialized variable is used in a computation. 5. What is the function of the dot operator? a. It serves to separate the integer portion from the fractional portion of a floating-point number. b. It allows one to access the data within an object when given a reference to the object. c. It allows one to invoke a method within an object when given a reference to the object. d. It is used to terminate commands, similar to the way a period terminates a sentence in English. e. Both B and C are correct. ANS: E The dot operator is appended directly after the object reference, followed by the data or method to which access is desired. In the case of data, the access may be for reading or writing. In the case of a method, the access is to allow one to invoke the method. The dot within a floating-point number is a decimal point and not a dot operator. 6. In Java, instantiation means a. b. c. d. e.

noticing the first time something is used creating a new object of the class creating a new alias for an existing object launching a method none of these

ANS: B Instantiation is the process of creating a new instance of an object. This usually is accomplished by using the new operator. In the case of Strings, new instances (instantiation) may be created just by using quotes in an expression. For example: String s; s = "A new string (instance)"; 7. Assume you write a program that uses the Random class but you fail to include an import statement for java.util.Random or java.util.*. What will happen when you attempt to compile and run your program? a. b. c. d.

The program won't run but it will compile with a warning about missing the class. The program won't compile and you'll receive a syntax error about the missing class. The program will compile but you'll receive a warning about the missing class. The program will encounter a run-time error when it attempts to access any member of the Random class. e. none of these ANS: B The missing class means that there will be undefined variables and/or methods. The compiler will detect these and will issue error messages. Your program won't be executable. 8. In the StringMutation program shown in Listing 3.1, if phrase is initialized to "Einstein", what will Mutation # 3 yield if mutation1 = phrase.concat(".")? a. b. c. d. e.

Einstein. EINSTEIN. XINSTXIN. einstein. xinstxin.

ANS: C Mutation #2 changes every letter to upper case. Then Mutation #3 replaces Es with Xs. 9. Which of the following will yield a pseudorandom number in the range [-5, +5), given: Random gen = new Random(); a. b. c. d. e.

gen.nextFloat()*5 gen.nextFloat()*10-5 gen.nextFloat()*5-10 gen.nextInt()*10-5 gen.nextInt(10)-5

ANS: B nextFloat yields a pseudorandom number in the range [0, 1); multiplying by 10 yields numbers in the range [0, 10); subtracting 5 yields numbers in the range [-5, 5). 10. What will be displayed by the following command? System.out.println(Math.pow(3, 3-1)); a. 9 b. 8 c. 6

d. 4 e. 27 ANS: A This evaluates to Math.pow(3, 2) which is 3^2 which is 9 11. Given the following two lines of code, what can be said about s1 and s2? String s1 = "testing" + "123"; String s2 = new String("testing 123"); a. b. c. d. e.

s1 and s2 are both references to the same String object. the line declaring s1 is legal in Java; the line declaring s2 will produce a syntax error. s1 and s2 are references to different String objects. s1 and s2 will compare "equal." None of the above

ANS: C Both declarations are legal Java. s1 is a String reference, and it is initialized to the String "testing123". s2 is a String reference, and it is initialized to the String "testing 123". Note the space between the "testing" and the "123". So the two Strings are not equal. 12. An alias is when a. b. c. d. e.

two different reference variables refer to the same physical object two different numeric variables refer to the same physical object two different numeric variables contain identical values two variables have the same name None of these

ANS: A An "alias" occurs when there are two or more references to the same physical object so that by following either reference, one can read/write/modify the object. 13. An API is a. b. c. d. e.

an Abstract Programming Interface an Application Programmer's Interface an Application Programming Interface an Abstract Programmer's Interface an Absolute Programming Interface

ANS: C An API is an Application Programming Interface. This is a collection of related classes that have been built for specific purposes. APIs usually reside in a class library. 14. Java.text's NumberFormat class includes methods that a. b. c. d. e.

allow you to format currency allow you to format percentages round their display during the formatting process truncate their display during the formatting process A, B, C, but not D

ANS: E

NumberFormat always rounds; it never truncates. And it does provide methods for both currency and percentages. 15. The advantages of the DecimalFormat class compared to the NumberFormat class include a. b. c. d. e.

precise control over the number of digits to be displayed control over the presence of a leading zero the ability to truncate values rather than round them the ability to display a percent sign (%) automatically at the beginning of the display only A and B

ANS: E While DecimalFormat does provide far more control than NumberFormat, truncation remains in the hands of the programmer via one or more of the Math methods. The % symbol would appear at the end of the display, not the beginning. 16. The advantage(s) of the Random class's pseudorandom number generators, compared to the Math.random method, is(are) that a. b. c. d. e.

you may create several random number generators the generators in Random are more efficient than the one in Math.random you can generate random ints, floats, and ints within a range you can initialize and reinitialize Random generators all except B are true

ANS: E The efficiency of all the random number generators are the same. The advantages of Random generators over Math.random include all the other properties. 17. The String class's compareTo method a. b. c. d. e.

compares two strings in a case-independent manner yields true or false yields 0 if the two strings are identical rerturns 1 if the first string comes lexically before the second string None of these

ANS: C compareTo yields 0 if the two strings are identical, -1 if the first string comes lexically before the second, +1 if the first string comes lexically after the second. 18. Which statement is true, given the following code fragment? String strA = "aBcDeFg"; String strB = strA.toLowerCase(); strB = strB.toUpperCase(); string strC = strA.toUpperCase(); a. b. c. d. e.

strB.equals(strC) would be true strB.compareTo(strC) would yield 0 strA.equals(strC) would be true strA.compareTo(strC) would yield 0 None of these

ANS: B strB contains the uppercase forms of all the letters in strA; so does strC. So compareTo would yield 0, indicating equality. 19. In addition to providing a mechanism to convert primitive data into objects, what else do the wrapper classes provide? a. b. c. d. e.

enumerations static constants arrays to contain the data exceptions None of these

ANS: B The wrapper classes also provide static constants, like MIN_VALUE and MAX_VALUE (the smallest and largest ints). 20. Which is now the preferred approach for developing Java programs that use graphics and GUIs? a. b. c. d. e.

Swing AWT JavaFX API All of these are preferred approaches

ANS: C The JavaFX API has now replaced the AWT and Swing for developing graphical programs. 21. In a development environment that fully supports JavaFX, which of the following is true? a. The launch method of the scene class is called automatically. b. The launch method of the Application class is called automatically. c. Since the launch method is called automatically, you do not need to write the main method. d. Since the launch method is called automatically, you do not need to call it in the main method. e. Both B and C are true ANS: E 22. Which of the following packages includes classes that represent shapes in JavaFX? a. b. c. d. e.

javafx.scene.shape javafx.shape.scene javafx.shapes javafx.stage.shape javafx.stage.scene

ANS: A 23. Write a declaration for a Rectangle named squareShape that is 400 pixels wide, 400 pixels high, and its upper-left corner position is at point (50, 50). a. Rectangle squareShape = new squareShape(50, 50, 400, 400);

b. c. d. e.

squareShape = new Rectangle(50, 50, 400, 400); Rectangle squareShape = new Rectangle(50, 400, 50, 400); Rectangle squareShape = new Rectangle(50, 50, 400, 400); Rectangle = new squareShape(400, 400, 50, 50);

ANS: D 24. What does the following code fragment do? Circle circle = new Circle(100, 100, 50); circle.setFill(Color.GREEN); Rectangle rectangle = new Rectangle(70, 70, 225, 75); rectangle.setStroke(Color.BLUE); rectangle.setStrokeWidth(2); rectangle.setFill(null); a. It creates a green circle, centered at coordinates (100, 100). b. It creates a rectangle which overlaps the circle since its upper-left corner is at coordinates (70, 70) and its dimensions are 225 X 75. c. Since the rectangle's fill color is set to null, the circle will be visible through the rectangle. d. The rectangle will have a blue border. e. All of these are true. ANS: E Shapes are drawn in the order they are added to a container such as a group or pane. So, to make one shape appear in front of another, it should be added after it. If the fill color of the rectangle is set to null, anything behind it will show through. PROBLEM 1. Rewrite the following five assignment statements into a single statement using prefix and postfix increment and decrement operators as necessary. Assume all variables are int variables. x = y + 1; y = y + 1; z = z - 1; x = x - z; x = x + 1; ANS: x = (y++ + 1) - (--z) + 1; 2. Consider the condition (x == y). How is this handled if x and y are primitive types? How is this handled if x and y are objects? ANS: If x and y are primitive types, then the values stored in them are compared and true is returned if the two values are equal. If they are objects, then the object that each references are compared. If they are the same object, it returns true, otherwise it returns false.

3. Given two String variables, s1 and s2, is it possible for (s1 != s2)to be true while (s1.equals(s2)) is also true? Why or why not? ANS: The condition (s1 != s2) means that s1 and s2 are references to two distinct objects. It says nothing about the contents of the referenced objects. So, the contents of s1 may well be identical or different from the contents of s2. Therefore it is quite possible that (s1.equals(s2)) is true while (s1 != s2) is also true. 4. What is a wrapper class? Why are wrapper classes useful? ANS: A wrapper class is a class that allows you to embed one piece of primitive data within an object. There are methods for extracting the data from the object. Wrapper classes are useful where you have methods (or constructors) that only accept objects and not primitive data. By wrapping the primitive data within an object the functionality of the method (and its class) may be accessed. Problem Ch 03-1 Assume an interactive Java program which asks the user for his/her first name and last name, and outputs the user's initials. 5. Refer to Problem Ch 03-1. For the program to get a name interactively a Scanner object must be instantiated. Write the Java statement to do this. ANS: Scanner scan = new Scanner(System.in); 6. Refer to Problem Ch 03-1. Write a statement using a Scanner method to get the first name interactively. ANS: firstName = scan.nextLine(); 7. Refer to Problem Ch 03-1. Write a method to extract the initial from the first name. ANS: firstInitial = firstName.substring(0,1); 8. Refer to Problem Ch 03-1. Write a statement to guarantee that the initial will be a capital letter. ANS: firstInitial = firstInitial.toUpperCase();

9. What is autoboxing? ANS: Autoboxing provides automatic conversions between primitive values and corresponding wrapper objects. It makes your code shorter by relieving you of the need to provide explicit wrapping of primitive values and explicit extraction of primitive values. 10. Write a statement to create a Color object equivalent to Color.ORANGE using the rgb method. ANS: Color orange = Color.rgb(255, 165, 0); 11. Why is it often a good idea to group particular elements together in a scene? ANS: This makes it much easier to apply transformations such as rotations and position shifts to an entire group at once.

Java Software Solutions, 9e (Lewis/Loftus) Chapter 3 Using Classes and Objects TRUE/FALSE 1. Only difficult programming problems require a pseudocode solution before the programmer creates the program itself. ANS: F Some form of design should be created for all problems before the program is written, with the possible exception of only the most trivial of problems. The form of the design may vary. For instance, programmers in the 1960s and 1970s often used flowcharts instead of pseudocode. 2. You may apply the prefix and postfix increment and decrement operators to instances of the Integer class. ANS: F These operators may only be applied to numeric data. An instance of a class is an object and and not a piece of primitive data. 3. In Java, the symbol "=" and the symbol "==" are used interchangeably. ANS: F "=" is used for assignment statements while "==" is used to test equality in conditional statements. 4. When comparing any primitive type of variable, the == operator should always be used to test if two values are equal. ANS: F This is true of int, short, byte, long, char and boolean, but not of double or float variables. If two double variables, x and y, are being tested, (x == y) is true only if they are exactly equal to the last decimal point. It is common instead to compare these two values but allow for a small difference in value. For instance, if THETA = 0.000001, we might test x and y by (x y <= THETA) instead of (x == y) to get a better idea of whether they are close enough to be considered equal. 5. These two ways to set up a String will yield identical results: String my_string = "12345"; String my_string = 12345; ANS: F In fact, the second statement won't even compile! The second statement will receive a syntax error about incompatible types. There is no automatic conversion from a number to a String. 6. These two ways to set up a String will yield identical results: String my_string = new String("a bunch of words");

MULTIPLE CHOICE 1. In Java a variable may contain a. b. c. d. e.

a value or a reference a package a method a class Any of these

3. Which properties are true of String objects? a. b. c. d. e.

4. What happens if you attempt to use a variable before it has been initialized? a. b. c. d. e.

noticing the first time something is used creating a new object of the class creating a new alias for an existing object launching a method none of these

Einstein. EINSTEIN. XINSTXIN. einstein. xinstxin.

gen.nextFloat()*5 gen.nextFloat()*10-5 gen.nextFloat()*5-10 gen.nextInt()*10-5 gen.nextInt(10)-5

ANS: A An "alias" occurs when there are two or more references to the same physical object so that by following either reference, one can read/write/modify the object. 13. An API is a. b. c. d. e.

an Abstract Programming Interface an Application Programmer's Interface an Application Programming Interface an Abstract Programmer's Interface an Absolute Programming Interface

allow you to format currency allow you to format percentages round their display during the formatting process truncate their display during the formatting process A, B, C, but not D

ANS: E

compares two strings in a case-independent manner yields true or false yields 0 if the two strings are identical rerturns 1 if the first string comes lexically before the second string None of these

strB.equals(strC) would be true strB.compareTo(strC) would yield 0 strA.equals(strC) would be true strA.compareTo(strC) would yield 0 None of these

enumerations static constants arrays to contain the data exceptions None of these

Swing AWT JavaFX API All of these are preferred approaches

javafx.scene.shape javafx.shape.scene javafx.shapes javafx.stage.shape javafx.stage.scene

b. c. d. e.

Java Software Solutions, 9e (Lewis/Loftus) Chapter 4 Writing Classes TRUE/FALSE 1. Java methods can only return primitive types. ANS: F Java methods can also return objects such as String. 2. Formal parameters are those that appear in the method call and actual parameters are those that appear in the method header. ANS: F The question has the two definitions reversed. Formal parameters are those that appear in the method header, actual parameters are the parameters in the method call (those being passed to the method). 3. All Java classes must contain a main method which is the first method executed when the Java class is called on. ANS: F Only the driver program requires a main method. The driver program is the one that is first executed in any Java program (except for Applets), but it may call upon other classes as needed, and these other classes do not need main methods. 4. Java methods can return more than one item if they are modified with the reserved word continue, as in public continue int foo() {...} ANS: F All Java methods return a single item, whether it is a primitive data type an object, or void. The reserved word continue is used to exit the remainder of a loop and test the condition again. 5. The following method header definition will result in a syntax error: public void aMethod(); ANS: T The reason for the syntax error is because it ends with a ; symbol. It instead needs to be followed by {} with 0 or more instructions inside of the brackets. An abstract method will end with a ; but this header does not define an abstract method. 6. A method defined in a class can access the class's instance data without needing to pass them as parameters or declare them as local variables. ANS: T

The instance data are globally available to all of the class's methods and therefore the methods do not need to receive them as parameters or declare them locally. If variables of the same name as instance data were declared locally inside a method then the instance data would be "hidden" in that method because the references would be to the local variables. 7. The interface of a class is based on those data instances and methods that are declared public. ANS: T The interface is how an outside agent interacts with the object. Interaction is only available through those items declared to be public in the class's definition. 8. Defining formal parameters requires including each parameter's type. ANS: T In order for the compiler to check to see if a method call is correct, the compiler needs to know the types for the parameters being passed. Therefore, all formal parameters (those defined in the method header) must include their type. This is one element that makes Java a strongly typed language. 9. Every class definition must include a constructor. ANS: F Java allows classes to be defined without constructors. However, there is a default constructor that is used in such a case. 10. While multiple objects of the same class can exist, in a given program there can only be one version of each class. ANS: T A class is an abstraction; that is, it exists as a definition, but not as a physical instance. Physical instances are created when an object is instantiated using new. Therefore, there can be many objects of type String, but only one String class. 11. A constructor may contain a return statement so long as no value (or expression) is returned. ANS: T Constructors may contain non-value-returning return statements. Doing so is discouraged, but it is legal. 12. An object should be encapsulated in order to guard its data and methods from inappropriate access. ANS: T Encapsulation is the concept that objects should be protected from accidental (or purposeful) misuse. 13. Accessors and mutators provide mechanisms for controlled access to a well-encapsulated class.

ANS: T Accessors provide read access to variables that otherwise would be inaccessible. Mutators provide write access to otherwise inaccessible variables. 14. A GUI control sets up an event but it is the programmer who writes the code for the event handler which executes when an event occurs. ANS: T 15. Regarding the software failure described at the Denver International Airport in the text, it is critical to factor in errors and inefficiencies that alway occur in a complex system. ANS: T A good system is designed using a well-built systems analysis and design methodology that helps reduce the maintenance portion of the system's lifecycle. 16. Because an Image cannot directly be added to a container, it must be displayed using an ImageView object. ANS: T MULTIPLE CHOICE 1. The behavior of an object is defined by the object's a. b. c. d. e.

instance data constructor visibility modifiers methods All of these

ANS: D The methods dictate how the object reacts when it is passed messages. Each message is implemented as a method, and the method is the code that executes when the message is passed. The constructor is one of these methods but all of the methods combined dictate the behavior. The visibility modifiers do impact the object's performance indirectly. 2. The relationship between a class and an object is best described as a. b. c. d. e.

classes are instances of objects objects are instances of classes objects and classes are the same thing classes are programs while objects are variables objects are the instance data of classes

ANS: B Classes are definitions of program entities that represent classes of things/entities in the world. Class definitions include instance data and methods. To use a class, it is instantiated. These instances are known as objects. So, objects are instances of classes. Program code directly interacts with objects, not classes.

3. To define a class that will represent a car, which of the following definition is most appropriate? a. b. c. d. e.

private class car public class car public class Car public class CAR. private class Car

ANS: C Classes should be defined to be public so that they can be accessed by other classes. And following Java naming convention, class names should start with a capital letter and be lower case except for the beginning of each new word, so Car is more appropriate than car or CAR.

4. In order to preserve encapsulation of an object, we would do all of the following except for which one? a. b. c. d. e.

make the instance data private define the methods in the class to access and manipulate the instance data make the methods of the class public make the class final all of these preserve encapsulation

ANS: D Encapsulation means that the class contains both the data and the methods needed to manipulate the data. In order to preserve encapsulation properly, the instance data should not be directly accessible from outside of the classes, so the instance data are made private and methods are defined to access and manipulate the instance data. Further, the methods to access and manipulate the instance data are made public so that other classes can use the object. The reserved word final is used to control inheritance and has nothing to do with encapsulation. 5. If a method does not have a return statement, then a. b. c. d. e.

it will produce a syntax error when compiled it must be a void method it cannot be called from outside the class that defined the method it must be defined to be a public method it must be an int, double, float, or String method

ANS: B All methods are implied to return something and therefore there must be a return statement. However, if the programmer wishes to write a method that does not return anything, and therefore does not need a return statement, then it must be a void method (a method whose header has void as its return type).

6. Which of the following reserved words in Java is used to create an instance of a class? a. b. c. d. e.

class public public or private (can use either) import new

ANS: E

7. Consider a sequence of method invocations as follows: main calls m1, m1 calls m2, m2 calls m3, and then m2 calls m4, m3 calls m5. If m4 has just terminated, what method will resume execution? a. b. c. d. e.

m1 m2 m3 m5 main

ANS: B Once a method terminates, control resumes with the method that called that method. In this case, m2 calls m4 so that when m4 terminates, m2 is resumed. 8. A variable whose scope is restricted to the method where it was declared is known as a(n) a. b. c. d. e.

parameter global variable local variable public instance data private instance data

ANS: C Local variables are those that are "local" to the method in which they have been declared; that is, they are accessible only inside that method. Global variables are those that are accessible from anywhere, while parameters are the variables passed into a method. Instance data can be thought of as global variables for an entire object. 9. A class's constructor usually defines a. b. c. d. e.

how an object is initialized how an object is interfaced the number of instance data in the class the number of methods in the class if the instance data are accessible outside of the object directly

ANS: A The constructor should be used to "construct" the object, that is, to set up the initial values of the instance data. This is not essential, but is typically done. The interface of an object is dictated by the visibility modifiers used on the instance data and methods. 10. Having multiple class methods of the same name where each method has a different number of or type of parameters is known as a. b. c. d. e.

encapsulation information hiding tokenizing importing method overloading

ANS: E When methods share the same name, they are said to be overloaded. The number and type of parameters passed in the message provides the information by which the proper method is called. 11. Instance data for a Java class

a. b. c. d. e.

are limited to primitive types are limited to Strings are limited to objects (e.g., Strings, classes defined by other programmers) may be primitive types or objects but objects must be defined to be private may be primitive types or objects

ANS: E The instance data are the entities that make up the class and may be any type available whether primitive or object, and may be public or private. By using objects as instance data, it permits the class to be built upon other classes. This relationship where a class has instance data that are other classes is known as a has-a relationship. 12. An example of passing a message to a String where the message has a String parameter would occur in which of the following messages? a. b. c. d. e.

length substring equals toUpperCase None of these; it is not possible to pass a String as a parameter to a String

ANS: C The length and toUpperCase messages do not have parameters and substring has two int parameters. For equals, a String must be passed as a parameter so that the String receiving the message can be compared to the String passed as a parameter. 13. Consider a Rational class designed to represent rational numbers as a pair of ints, along with methods reduce (to reduce the rational to simplest form), gcd (to find the greatest common divisor of two ints), as well as methods for addition, subtraction, multiplication, and division. Why should the reduce and gcd methods be declared to be private? a. b. c. d. e.

because they will never be used because they will only be called from methods inside Rational because they will only be called from the constructor of Rational because they do not use any of the Rational instance data This is incorrect; they should be declared as public

ANS: B All items of a class that are declared to be private are only accessible to entities within that class, whether they are instance data or methods. In this case, since these two methods are only called from other methods (including the constructor) of Rational, they are declared private to promote information hiding to a greater degree. Note that answer C is not a correct answer because the reduce method calls the gcd method, so one of the methods is called from a method other than the constructor. 14. Given the method defined here, which of the following method calls is legal? public void foo(int a, int b) a. foo(0, 0.1); b. foo(0/1, 2*3); c. foo(0);

d. foo(); e. foo(1+2, 3*0.1); ANS: B The only legal method call is one that passes twoint parameters. In the case of answer B, 0 / 1 is an int division (equal to 0) and 2 * 3 is an int multiplication. So this is legal. The answers for A and E contain two parameters, but the second of each is a double. The answers for C and D have the wrong number of parameters. 15. Given the method defined here, which of the following method calls is legal? public void doublefoo(double x) a. b. c. d. e.

doublefoo(0); doublefoo(0.555); doublefoo(0.1 + 0.2); foo(0.1, 0.2); all except D are legal

ANS: E In the case of A, the value 0 (an int) is widened to a double. In the case of C, the addition is performed yielding 0.3 and then doublefoo is called. The parameter list in D is illegal since it contains two double parameters instead of 1. 16. In a UML diagram for a class a. b. c. d. e.

classes are represented as rectangles there may be a section containing the name of the class there may be a section containing the attributes of the class there may be a section containing the methods of the class All of these

ANS: E Those four attributes correctly describe a UML representation of a class. 17. The expressions that are passed to a method in an invocation are called a. b. c. d. e.

actual parameters formal parameters formal arguments formals Any of these

ANS: A The formals (formal parameters, formal arguments) are those given in a method's header, where it is declared. The actual parameters (actuals, actual arguments) are the expressions that actually are transmitted to a method in an invocation. 18. What happens if you declare a class constructor to have a void return type? a. b. c. d.

You will most likely receive a syntax error. The program will compile with a warning but you'll get a run-time error. There is nothing wrong with declaring a constructor with a void return type. The class's default constructor will be used instead of the one you're declaring.

e. None of these ANS: A It is a syntax violation to declare a constructor with any type, even void, so you'll receive a syntax error. 19. Which of the following is not a kind of object that is used to create a graphical user interface in JavaFX? a. b. c. d. e.

control event image event handler All of these are objects used to create a GUI in JavaFX

ANS: A An image is not a kind of object used to create a GUI even though it is an object. It can only be displayed with an ImageView JavaFX node. 20. The software failure at the Denver International Airport's baggage handling system is a good example of a. how a large system can be obsolete by the time it is developed b. how designers sometimes have too much faith in the technology they are using c. how failures are often a result of multiple variables caused by a system as a whole in actual operation d. how the use of a centralized computer is unrealistic in today's distributed processing e. All of these ANS: E All of these are good examples of why software fails. 21. Visibility modifiers include a. b. c. d. e.

public, private public, private, protected public, private, protected, final public, protected, final, static public, private, protected, static

ANS: B public, private, protected control the visibility of variables and methods. final controls whether a variable, method, or class can be further changed or overridden; it does not control visibility. static controls whether a variable or method is associated with instances of a class or the class itself. Class Definition Ch 04-1 import java.text.DecimalFormat; public class Student { private String name; private String major; private double gpa;

private int hours; public Student(String newName, String newMajor, double newGPA, int newHours) { name = newName; major = newMajor; gpa = newGPA; hours = newHours; } public String toString() { // xxxx needs to be replaced DecimalFormat df = new DecimalFormat("xxxx"); return name + "\n" + major + "\n" + df.format(gpa) + "\n" + hours } } 22. Refer to Class Definition Ch 04-1: Which of the following patterns should be used in place of "xxxx" when instantiating df so that the gpa to be output is in typical form (like 3.810)? a. b. c. d. e.

"#.###" "#.0" "0.#" "0.000" "0.0##"

ANS: D GPA is traditionally output as a 4 digit value with the decimal point after the first digit. Digits are output no matter if they are 0 or otherwise. So, to get 3.810, with the trailing 0, or to get 0.813 with the leading 0, the format must be "0.000" rather than "#.###". 23. Refer to Class Definition Ch 04-1: Which of the following could be used to instantiate a new Student s1? a. Student s1 = new Student(); b. s1 = new Student(); c. Student s1 = new Student("Jane Doe", "Computer Science", 3.333, 33); d. new Student s1 = ("Jane Doe", "Computer Science", 3.333, 33); e. new Student(s1); ANS: C To instantiate a class, the object is assigned the value returned by calling the constructor preceded by the reserved word new, as in new Student(). The constructor might require parameters, and for Student, the parameters must be two String values, a double, followed by an int. 24. Refer to Class Definition Ch 04-1: Assume that another method has been defined that will compute and return the student's class rank (Freshman, Sophomore, etc). It is defined as: public String getClassRank()

Given that s1 is a student, which of the following would properly be used to get s1's class rank? a. b. c. d. e.

s1 = getClassRank(); s1.toString(); s1.getHours(); s1.getClassRank(); getClassRank(sq);

ANS: D To call a method of an object requires passing that object a message which is the same as the method name, as in object.methodname(parameters). In this situation, the object is s1, the method is getClassRank, and this method expects no parameters. Answers A and E are syntactically illegal while answer B returns information about the Student but not his/her class rank, and there is no getHours method so C is also syntactically illegal. 25. Refer to Class Definition Ch 04-1: Another method that might be desired is one that updates the student's number of credit hours. This method will receive a number of credit hours and add these to the student's current hours. Which of the following methods would accomplish this? a. public int updateHours() { return hours; } b. public void updateHours() { hours++; } c. public updateHours(int moreHours) { hours += moreHours; } d. public void updateHours(int moreHours) { hours += moreHours; } e. getClassRank(sq);public int updateHours(int moreHours) { return hours + moreHours; } ANS: D This method will receive the number of new hours and add this to the current hours. The method in D is the only one to do this appropriately. Answer C is syntactically invalid since it does not list a return type. The answer in E returns the new hours, but does not reset hours appropriately.

2. When reasoning about a car, we use such information as its make and model, year, color, cost (or worth), number of miles, gas mileage, insurance cost, and so forth. Consider a program that will attempt to determine how practical a car might be on a road trip. Which of these types of information might you use in your program as instance data? Provide a justification for your selection. ANS: Because a road trip will include such factors as comfort and cost, we need to have instance data pertaining to the size of the vehicle, its gas mileage and its reliability. Size can be determined by make and model, reliability based on year and number of miles that the car has accrued, and cost based on gas mileage. The following would be a reasonable selection of instance data: model (maybe make as well), year, number of miles, gas mileage. 3. Write a portion of a class named Employee. An employee will have a name, ID number, position, and hourly wage. Define the instance data for this class. ANS: private String name, idnum, position; private double hourlyWages; 4. Explain why it would be a poor decision to make instance data public instead of private. Give an example of why this could result in a problem. ANS: If the instance data are public, then any other class can directly modify any of the instance data, and therefore the values would not be stored as intended. Class Definition Ch04-2 The following is from a class named BaseballPlayer. It contains the following data instances: private String name; private String position; private int numAtBats; private int numSingles; private int numDoubles; private int numTriples; private int numHomeRuns; private double battingAverage; 5. Refer to Class Definition Ch 04-2: Write the constructor which is passed the player's name and position. ANS: Notice that we not only initialize the instance data that were passed as parameters, but also all other data instances. public BaseballPlayer(String newName, String newPosition) { name = newName; position = newPosition;

numAtBats = 0; numSingles = 0; numDoubles = 0; numTriples = 0; numHomeRuns = 0; battingAverage = 0.0; } 6. Refer to Class Definition Ch 04-2: Write a toString method that returns the player's name, position, and batting average. formatted to have one digit to the left of the decimal and three digits to the right of the decimal. Assume DecimalFormat has been imported. ANS: public String toString() { DecimalFormat df = new DecimalFormat("0.000"); return name + "\t" + position + "\t" + df.format(battingAverage); } Class Definition Ch 04-3 Consider a class called Building. This class consists of a number of floors (numberOfFloors) for the building, a current floor for the elevator (current), a requested floor of a person waiting for the elevator (requestedFloor), and methods for constructing the building object, for moving the elevator one floor up, for moving the elevator one floor down, for requesting the elevator and for starting the elevator going. Assume that requestedFloor will be set to 0 if there are currently no requests being made (or the last request has already been fulfilled). 7. Refer to Class Definition Ch 04-3: Write the constructor for this class. ANS: public Building(int numFloors) { numberOfFloors = numFloors; current = 1; requestedFloor = 0; } 8. Refer to Class Definition Ch 04-3: What visibility modifiers would you use for the methods that move the elevator up one floor, move the elevator down one floor, that request the elevator, and that start the elevator moving? ANS: The request for the elevator will be performed from an outside object, so it should be public. It will set requestedFloor to a value, and then start the elevator going up or down. Moving the elevator up or down will be called from the method that starts the elevator. So, starting the elevator, moving the elevator up a floor, and moving the elevator down a floor should all be private as they will only be called from inside the class. Class Definition Ch 04-4

public class Box { double length; double width; double height; Box(double l, double w, double h) { length = l; width = w; height = h; }// Box( ) double volume() { return length * width * height; }// end volume() }// end class Box 9. Refer to Class Definition Ch 04-4: Write the statement to instantiate an Box object, blueBox, with a length of 6, width of 4, and height of 2. ANS: Box blueBox = new Box(6,4,2); 10. Refer to Class Definition Ch 04-4: Write a statement to output the volume of the blue box. ANS: System.out.println("Volume of the blue box is

"+blueBox.volume());

11. Refer to Class Definition Ch 04-4: Add a constructor to class Box for a cube which has only 1 parameter, side. ANS: Box(double s) { length = s; width = s; height = s; }// Box( ) 12. Refer to Class Definition Ch 04-4: Write a statement to instantiate a cube with a length of 3, width of 3, and height of 3. ANS: Box cube = new Box(3);

instance data constructor visibility modifiers methods All of these

classes are instances of objects objects are instances of classes objects and classes are the same thing classes are programs while objects are variables objects are the instance data of classes

3. To define a class that will represent a car, which of the following definition is most appropriate? a. b. c. d. e.

private class car public class car public class Car public class CAR. private class Car

4. In order to preserve encapsulation of an object, we would do all of the following except for which one? a. b. c. d. e.

make the instance data private define the methods in the class to access and manipulate the instance data make the methods of the class public make the class final all of these preserve encapsulation

6. Which of the following reserved words in Java is used to create an instance of a class? a. b. c. d. e.

class public public or private (can use either) import new

ANS: E

m1 m2 m3 m5 main

parameter global variable local variable public instance data private instance data

how an object is initialized how an object is interfaced the number of instance data in the class the number of methods in the class if the instance data are accessible outside of the object directly

encapsulation information hiding tokenizing importing method overloading

a. b. c. d. e.

length substring equals toUpperCase None of these; it is not possible to pass a String as a parameter to a String

doublefoo(0); doublefoo(0.555); doublefoo(0.1 + 0.2); foo(0.1, 0.2); all except D are legal

ANS: E Those four attributes correctly describe a UML representation of a class. 17. The expressions that are passed to a method in an invocation are called a. b. c. d. e.

actual parameters formal parameters formal arguments formals Any of these

control event image event handler All of these are objects used to create a GUI in JavaFX

public, private public, private, protected public, private, protected, final public, protected, final, static public, private, protected, static

"#.###" "#.0" "0.#" "0.000" "0.0##"

a. b. c. d. e.

s1 = getClassRank(); s1.toString(); s1.getHours(); s1.getClassRank(); getClassRank(sq);

PROBLEM 1. Assume method0 calls method1 and method2, method1 calls method3 which calls method4 and method5. Explain the chain of method calls (what order methods are called and from which method). ANS: method0 calls method1 which calls method3 which calls method4, method4 terminates and method3 calls method5, method5 terminates, method3 terminates, method1 terminates, method0 calls method2, method2 terminates, method0 terminates. 2. When reasoning about a car, we use such information as its make and model, year, color, cost (or worth), number of miles, gas mileage, insurance cost, and so forth. Consider a program that will attempt to determine how practical a car might be on a road trip. Which of these types of information might you use in your program as instance data? Provide a justification for your selection.

ANS: Because a road trip will include such factors as comfort and cost, we need to have instance data pertaining to the size of the vehicle, its gas mileage and its reliability. Size can be determined by make and model, reliability based on year and number of miles that the car has accrued, and cost based on gas mileage. The following would be a reasonable selection of instance data: model (maybe make as well), year, number of miles, gas mileage. 3. Write a portion of a class named Employee. An employee will have a name, ID number, position, and hourly wage. Define the instance data for this class. ANS: private String name, idnum, position; private double hourlyWages; 4. Explain why it would be a poor decision to make instance data public instead of private. Give an example of why this could result in a problem. ANS: If the instance data are public, then any other class can directly modify any of the instance data, and therefore the values would not be stored as intended. Class Definition Ch04-2 The following is from a class named BaseballPlayer. It contains the following data instances: private String name; private String position; private int numAtBats; private int numSingles; private int numDoubles; private int numTriples; private int numHomeRuns; private double battingAverage; 5. Refer to Class Definition Ch 04-2: Write the constructor which is passed the player's name and position. ANS: Notice that we not only initialize the instance data that were passed as parameters, but also all other data instances. public BaseballPlayer(String newName, String newPosition) { name = newName; position = newPosition; numAtBats = 0; numSingles = 0; numDoubles = 0; numTriples = 0;

numHomeRuns = 0; battingAverage = 0.0; } 6. Refer to Class Definition Ch 04-2: Write a toString method that returns the player's name, position, and batting average. formatted to have one digit to the left of the decimal and three digits to the right of the decimal. Assume DecimalFormat has been imported. ANS: public String toString() { DecimalFormat df = new DecimalFormat("0.000"); return name + "\t" + position + "\t" + df.format(battingAverage); } Class Definition Ch 04-3 Consider a class called Building. This class consists of a number of floors (numberOfFloors) for the building, a current floor for the elevator (current), a requested floor of a person waiting for the elevator (requestedFloor), and methods for constructing the building object, for moving the elevator one floor up, for moving the elevator one floor down, for requesting the elevator and for starting the elevator going. Assume that requestedFloor will be set to 0 if there are currently no requests being made (or the last request has already been fulfilled). 7. Refer to Class Definition Ch 04-3: Write the constructor for this class. ANS: public Building(int numFloors) { numberOfFloors = numFloors; current = 1; requestedFloor = 0; } 8. Refer to Class Definition Ch 04-3: What visibility modifiers would you use for the methods that move the elevator up one floor, move the elevator down one floor, that request the elevator, and that start the elevator moving? ANS: The request for the elevator will be performed from an outside object, so it should be public. It will set requestedFloor to a value, and then start the elevator going up or down. Moving the elevator up or down will be called from the method that starts the elevator. So, starting the elevator, moving the elevator up a floor, and moving the elevator down a floor should all be private as they will only be called from inside the class. Class Definition Ch 04-4 public class Box { double length; double width;

double height; Box(double l, double w, double h) { length = l; width = w; height = h; }// Box( ) double volume() { return length * width * height; }// end volume() }// end class Box 9. Refer to Class Definition Ch 04-4: Write the statement to instantiate an Box object, blueBox, with a length of 6, width of 4, and height of 2. ANS: Box blueBox = new Box(6,4,2); 10. Refer to Class Definition Ch 04-4: Write a statement to output the volume of the blue box. ANS: System.out.println("Volume of the blue box is

"+blueBox.volume());

Java Software Solutions, 9e (Lewis/Loftus) Chapter 5 Conditionals and Loops TRUE/FALSE 1. As in the other members of the C family of languages (C, C++, C#), Java interprets a zero value as false and a non-zero value as true. ANS: F Although the C family does, indeed, interpret zero and non-zero values in this manner, Java requires that the reserved constants true and false be used or that there be a logical evaluation using the relational and/or logical operators. 2. In Java, selection statements consist only of if and if-else statements. ANS: F This list omits switch statements. 3. In Java, the symbol "=" and the symbol "==" are used synonymously (interchangeably). ANS: F "=" is used for assignment statements while "==" is used to test equality. 4. The statement {} is a legal block. ANS: T A block consists of {, followed by zero or more Java statements, followed by }. So it is acceptable to have no statements between the brackets. Situations where this is necessary occur in Java, particularly when implementing methods of abstract classes, something you will study later. 5. The statement: if (a >= b) a++; else b--; will do the same thing as the statement: if (a < b) b--; else a++;. ANS: T We can reverse the if clause and else clause if we reverse the condition. The opposite condition of (a >= b) is (a < b) so this works out logically. Note that if we used the condition (a <= b) then the resulting statement would not do the same thing as the original if a >= b. 6. An if statement may or may not have an else clause, but an else clause must be part of an if statement.

ANS: T Java allows for either if or if-else statements. But else is only used as part of an if statement. 7. In order to compare int, float and double variables, you can use <, >, ==, !=, <=, >=, but to compare char and String variables, you must use compareTo(), equals()and equalsIgnoreCase(). ANS: F You can also directly compare char variables using <, >, ==, !=, <=, >=, but you must use compareTo(), equals() and equalsIgnoreCase() for any String comparisons. 8. Assume that boolean done = false, int x = 10, int y = 11, String s = "Help" and String t = "Goodbye". Then the expression (!done && x <= y) is true. ANS: T Since done is false, !done is true. Since 10 < 11, x <= y is true. Therefore, the entire expression is true. 9. Assume that boolean done = false, int x = 10, int y = 11, String s = "Help" and String t = "Goodbye". Then the expression (s.concat(t).length() < y) is true. ANS: F Concatenating s and t gives a String that is 11 characters long and 11 < 11 is false. 10. Assume that boolean done = false, int x = 10, int y = 11, String s = "Help" and String t = "Goodbye". Then the expression (done || s.compareTo(t) < 0) is true. ANS: F Both done is false and s.compareTo(t) < 0 is false since s does not come before t alphabetically, so the entire expression is false. 11. If you create an ArrayList without specifying the type of element, the ArrayList will store Object references which means you can put any type of object in the list. ANS: T 12. Regarding the Software Failure: The operators were warned that, although the Therac-25 had many safety precautions, it might be possible to accidentally overdose a patient. ANS: F Operators were told that there were so many safety precautions that it would be "virtually impossible" to overdose a patient.

MULTIPLE CHOICE 1. The idea that program instructions execute in order (linearly) unless otherwise specified through a conditional statement is known as a. b. c. d. e.

boolean execution conditional statements try and catch sequentiality flow of control

ANS: E The "flow of control" describes the order of execution of instructions. It defaults to being linear (or sequential) but is altered by using control statements like conditionals and loops. 2. Of the following if statements, which one correctly executes three instructions if the condition is true? a. if (x < 0) a = b * 2; y = x; z = a - y; b. { if (x < 0) a = b * 2; y = x; z = a - y; } c. if { (x < 0) a = b * 2; y = x; z = a - y ; } d. if (x < 0) { a = b * 2; y = x; z = a - y; } e. B, C, and D are all correct but not A ANS: D In order to have three instructions execute in the if clause when the condition is true, the three statements must be placed in a block following the condition. This is the syntax used in D. In A, there is no block. In B, the block is placed around the entire if statement such that the if clause is only a = b * 2; and the other two statements are not part of the if statement, but follow it. The syntax in C is illegal resulting in a syntax error. Don't forget that the structure of your code (how it lines up) is immaterial to the compiler.

3. Which of the sets of statements below will add 1 to x if x is positive and subtract 1 from x if x is negative but leave x alone if x is 0? a. if (x > 0) x++; else x--; b. if (x > 0) x++; else if (x < 0) x--; c. if (x > 0) x++; if (x < 0) x--; else x = 0; d. if (x == 0) x = 0; else x++; x--; e. x++; x--; ANS: B In B, if x is positive, x++ is performed, else if x is negative x-- is performed and otherwise, nothing happens, or x is unaffected. In A, C, D and E, the logic is incorrect. In A, x-- is done if x is not positive, thus if x is 0, x becomes -1 which is the wrong answer. In C, if x is positive, then x++ is performed. In either case, the next statement is executed and if x is not negative, the else clause is performed setting x to 0. So if x is positive, it becomes 0 after this set of code. In D, x++ and x-are both performed if x is not 0. And in E, this code does not attempt to determine if x is positive or negative, it just adds one and then subtracts one from x, leaving x where it started. 4. Consider the following code that will assign a letter grade of 'A', 'B', 'C', 'D', or 'F' depending on a student's test score. if (score >= 90) grade = 'A'; if (score >= 80) grade = 'B'; if (score >= 70) grade = 'C'; if (score >= 60) grade = 'D'; else grade = 'F'; a. b. c. d. e.

This code will work correctly in all cases. This code will work correctly only if the grade is greater than or equal to 60. This code will work correctly only if the grade is less than 60. This code will work correctly only if the grade is less than 70. This code will not work correctly under any circumstances.

ANS: D The problem with this code is that it consists of three if statements followed by one if-else statement, rather than a nested if-else statement. So the logic is improper. If the student's grade falls into the 'A' category, then all 4 conditions are true and the student winds up with a 'D'. If the student's grade falls into the 'B' category, then the first condition is false, but the next three are true and the student winds up with a 'D'. If the student's grade falls into the 'D' category, then the only condition that is true is the one that tests for 'D' and so the grade is assigned correctly. If the student's grade falls into the 'F' category, then none of the conditions are true and an 'F' is assigned correctly. So, only if the grade is less than 70 does the code work correctly.

5. Assume that count is 0, total is 20 and max is 1. The following statement will do which of the following? if (count != 0 && total / count > max) max = total / count; a. b. c. d.

The condition short circuits and the assignment statement is not executed. The condition short circuits and the assignment statement is executed without problem. The condition does not short circuit causing a division by zero error. The condition short circuits so that there is no division by zero error when evaluating the condition, but the assignment statement causes a division by zero error. e. The condition will not compile because it uses improper syntax. ANS: A Since count is 0, (count != 0) is false. Because the left-hand side of an && condition is false, the condition is short circuited, and so the right-hand side is not evaluated. Thus, a potential division by zero error is avoided. Because the condition is false, the statement max = total / count is not executed, again avoiding a potential division by zero error. 6. What is wrong, logically, with the following code? if (x > 10) System.out.println("Large"); else if (x > 6 && x <= 10) System.out.println("Medium"); else if (x > 3 && x <= 6) System.out.println("Small"); else System.out.println("Very small"); a. There is no logical error, but there is no need to have x <= 10 in the second conditional or x <= 6 in the third conditional. b. There is no logical error, but there is no need to have x > 6 in the second conditional or x > 3 in the third conditional. c. The logical error is that no matter what value x is, Very small is always printed out. d. The logical error is that no matter what value x is, Large is always printed out. e. There is nothing wrong with the logic at all. ANS: A Because this is a nested if-else statement, if (x>10)is true, then the first println statement is executed and the rest of the statement is skipped. If (x>10)is not true, then the first else clause is executed and the next if condition is tested. At this point, (x>10)is known to be false and therefore (x<=10)must be true, so there is no need to check this inequality. Similarly, if (x>6)is false, then the second else clause is executed and the third if condition is tested. However, (x<=6)must be true, so there is no need to check this inequality. 7. Consider the following outline of a nested if-else structure which has more if clauses than else clauses. Which of the statements below is true regarding this structure? if (condition1) if (condition2) statement1; else statement2;

a. Syntactically it is invalid to have more if clauses than else clauses b. statement2 will only execute if condition1 is false and condition2 is false c. statement2 will only execute if condition1 is true and condition2 is false d. statement2 will only execute if condition1 is false, it does not matter what condition2 is e. statement2 will never execute ANS: C The else clause must be matched to the most recent if statement. Therefore, the else goes with the if statement that tests condition2, not the if statement that tests condition1. So, if condition1 is true and condition2 is false, then statement2 will execute. 8. Assume that x and y are int variables with x = 5, y = 3, and a and d are char variables with a = 'a' and d = 'A', and examine the following conditions: Condition 1: Condition 2: Condition 3: Condition 4: a. b. c. d. e.

(x < y && x > 0) (a != d || x != 5) !(true && false) (x > y || a == 'A' || d != 'A')

all 4 conditions are true Only Condition 2 is true Condition 2 and Condition 4 are true only Conditions 2, 3,4 are all true, Conditions 1 is not all 4 conditions are false

ANS: D Condition 1 is not true because x < y is false, making the entire condition false. Since a != d is true, Condition 2 is true even though x != 5 is false. Condition 3 is true because (true && false) is false, but !false is true. Condition 4 is true because x > y is true, making the entire condition true. Therefore, Conditions 2, 3,4 are true while Condition 1 is false. 9. What does the break statement do? a. b. c. d. e.

ends a program transfers control out of the current control structure such as a loop or switch statement ends the current line of output, returning the cursor denotes the end of a switch statement indicated the end of a line when using System.out.print

ANS: B This is the exit statement that allows the programmer to exit a control structure from inside of that control structure. 10. If a break occurs within the innermost loop of a nested loop that is three levels deep a. just the innermost loop will be "broken" b. all loops are "broken" and execution continues from after the end of the loop c. all but the outermost loops are "broken" and execution continues from the next iteration of the outermost loop d. a syntax error is generated unless there are break or continue statements at each loop level

e. None of these are true ANS: A The innermost loop is broken, and execution continues from just after the end of that loop. 11. Which of the following are true about check boxes? a. b. c. d. e.

They may be checked or unchecked. You can allow more than one check box to be checked by the user at a given time. Check boxes are Java components. You can control whether they will be visible or not. All of these are true about check boxes

ANS: E 12. Every iterator a. b. c. d. e.

has a hasNext() method has a hasFirst()method has a hasNextInt()method has a isEmpty()method None of these

ANS: A Every iterator has a hasNext() method that is true if there are iteration elements that have yet to be processed. Every iterator also has a next() method that delivers the next element for processing. 13. If x is an int where x = 1, what will x be after the following loop terminates? while (x < 100) x *= 2; a. b. c. d. e.

2 64 100 128 None of these; this is an infinite loop

ANS: D With x = 1, the loop condition is true and the statement executes, doubling x, which is now 2. Since the loop condition is still true, the statement executes again, doubling x to 4. The condition remains true for the next 4 iterations, where x becomes 8, 16, 32 and 64. Since x < 100 is still true when x = 64, the loop iterates again and x becomes 2*64 = 128. Now, x < 100 is no longer true and the loop terminates with x = 128. 14. If x is an int where x = 0, what will x be after the following loop terminates? while (x < 100) x *= 2; a. b. c. d. e.

2 64 100 128 None of these; this is an infinite loop

ANS: E Since x starts at 0, x *= 2; results in 0 * 2, or x = 0. Since x remains 0, x <100 remains true, and the loop repeats. x continues to be 0 and so the condition never changes to false, and thus the loop never terminates. 15. How many times will the following loop iterate? int x = 10; while (x > 0) { System.out.println(x); x--; } a. b. c. d. e.

0 once 9 times 10 times 11 times

ANS: D Since the condition is tested before the loop body executes, the loop will not execute once x == 0. So, the loop iterates for x = 10, x = 9, ..., x = 1, or 10 times. 16. Which type of GUI control would be best to use if you wanted the user to select one date from a list of three possible dates to take an exam? a. b. c. d. e.

check boxes because they are used for mutually exclusive options radio buttons because they are used for mutually exclusive options either check boxes or radio buttons because either are used for mutually exclusive options neither check boxes nor radio buttons can be used for mutually exclusive options There is no way to force a user to select only one option from a list; this must be done with a text input box.

ANS: B Code Segment Ch 05-1 if (a > 0) if (b < 0) x = x + 5; else if (a > 5) x = x + 4; else x = x + 3; else x = x + 2; 17. Refer to Code Segment Ch 05-1. If x is currently 0, a = 5 and b = 5, what will x become after the statement shown is executed? a. 0 b. 2 c. 3

d. 4 e. 5 ANS: C Since a > 0 is true, the next condition is checked. Since b < 0 is false, the else clause for this condition is executed. Since a > 5 is false the else clause for this condition is executed, which is x = x + 3. Therefore, 3 is added to x, so it is now 3. 18. Refer to Code Segment Ch 05-1. If x is currently 0, a = 0 and b = -5, what will x become after the statement shown is executed? a. b. c. d. e.

0 2 3 4 5

ANS: B Since a > 0 is not true, the else clause for this condition is executed which is x = x + 2 x is now 2. 19. Refer to Code Segment Ch 05-1. If x is currently 0, a = 1 and b = -1, what will x become after the statement shown is executed? a. b. c. d. e.

0 2 3 4 5

ANS: E Since a > 0 is true, the if clause for this condition is executed which is another if statement. Its condition, b < 0 is true so its if clause is executed which is x = x + 5, so now x is 5.

20. As introduced in the Software Failure, the terminology "risk analysis" means a. how willing you are to risk the loss of several key programmers working on your project b. how much you are willing to risk that a particular piece of software you are developing still contains an error or errors c. how willing you are to risk that your software will fail once implemented d. how willing you are to risk that the machines on which your software will run will not work e. None of these ANS: B The terminology "risk analysis" pertains explicitly to the risks a developer is willing to take that a piece of software developed will still contain errors at the time of implementation. PROBLEM 1. Rewrite the following set of if statements using a nested if-else structure.

if (score >= 90) grade = 'A'; if (score >= 80 && score < 90) grade = 'B'; if (score >= 70 && score < 80) grade = 'C'; if (score >= 60 && score < 70) grade = 'D'; if (score < 60) grade = 'F'; ANS: if (score >= 90) grade = 'A'; else if (score >= 80) grade = 'B'; else if (score >= 70) grade = 'C'; else if (score >= 60) grade = 'D'; else grade = 'F'; 2. A truth table shows, for the various true or false values of boolean variables, what the result of a boolean condition is. Fill in the following truth table. Assume that a, b and c are boolean variables. a false false false false true true true true

b false false true true false false true true

c false true false true false true false true

a && (!b

|| c)

b false false true true false false true true

c false true false true false true false true

a && (!b false false false false true true false true

|| c)

ANS: a false false false false true true true true

3. A truth table shows, for the various true or false values of boolean variables, what the result of a boolean condition is. Fill in the following truth table. Assume that a, b and c are boolean variables. a false false false false true true true true ANS:

b false false true true false false true true

c false true false true false true false true

!(a && b) ||

!(a && c)

a false false false false true true true true

b false false true true false false true true

c false true false true false true false true

!(a && b) ||

!(a && c)

true true true true true true true false

4. Explain what is meant by short circuiting and provide an example of short circuiting a condition with && and provide an example of short circuiting a condition with ||. ANS: Short circuiting is when a boolean expression does not have to be completely evaluated because the final answer is determined with just a partial evaluation. This can occur in an expression with && if one part of the expression evaluates to false, and in an expression with || if one part of the expression evaluates to true. Examples: 1. (x != 0) && (sum / x > 100) can be short circuited if x != 0 is false, preventing a division by zero error. 2. (a.equals("yes") || a.equals("no")) can be short circuited if a is equal to "yes" so that the computer does not waste time in testing a.equals("no"). 5. The following code has a syntax error immediately before the word else. What is the error and why does it arise? Fix the code so that this statement is a legal if-else statement. if (x < 0); x++; else x--; ANS: The error is "else without if" and it arises because of the ; after the condition but before x++. The Java compiler determines that the if clause is in fact ; (no statement) and that x++; is a statement that follows the if statement. Therefore, since x++; is not part of the if statement, the else is felt to be an else without an if, and that is why the error arises. The statement should be: if (x < 0) x++; else x--; 6. String s1 is said to overlap String s2 if all of the characters in s1 also appear in s2. Write a set of code that will set the boolean variable overlap to true if s1 overlaps s2 and false otherwise. Assume both s1 and s2 have already been input. ANS: boolean overlap = true; int j = 0; while (overlap && j < s1.length()) { boolean found = false; int k = 0; while (!found && k < s2.length()) if (s2.charAt(k) == s1.charAt(j))

found = true; else k++; if (!found) overlap = false; j++; }

MULTIPLE CHOICE 1. The idea that program instructions execute in order (linearly) unless otherwise specified through a conditional statement is known as a. b. c. d. e.

boolean execution conditional statements try and catch sequentiality flow of control

a. if (x > 0) x++; else x--; b. if (x > 0) x++; else if (x < 0) x--; c. if (x > 0) x++; if (x < 0) x--; else x = 0; d. if (x == 0) x = 0; else x++; x--; e. x++; x--; ANS: B In B, if x is positive, x++ is performed, else if x is negative x-- is performed and otherwise, nothing happens, or x is unaffected. In A, C, D and E, the logic is incorrect. In A, x-- is done if x is not positive, thus if x is 0, x becomes -1 which is the wrong answer. In C, if x is positive, then x++ is performed. In either case, the next statement is executed and if x is not negative, the else clause is performed setting x to 0. So if x is positive, it becomes 0 after this set of code. In D, x++ and x-are both performed if x is not 0. And in E, this code does not attempt to determine if x is positive or negative, it just adds one and then subtracts one from x, leaving x where it started. 4. Consider the following code that will assign a letter grade of 'A', 'B', 'C', 'D', or 'F' depending on a student's test score. if (score >= 90) grade = 'A'; if (score >= 80) grade = 'B'; if (score >= 70) grade = 'C'; if (score >= 60) grade = 'D'; else grade = 'F'; a. b. c. d. e.

max = total / count; a. b. c. d.

c. statement2 will only execute if condition1 is true and condition2 is false d. statement2 will only execute if condition1 is false, it does not matter what condition2 is e. statement2 will never execute ANS: C The else clause must be matched to the most recent if statement. Therefore, the else goes with the if statement that tests condition2, not the if statement that tests condition1. So, if condition1 is true and condition2 is false, then statement2 will execute. 8. Assume that x and y are int variables with x = 5, y = 3, and a and d are char variables with a = 'a' and d = 'A', and examine the following conditions: Condition 1: Condition 2: Condition 3: Condition 4: a. b. c. d. e.

(x < y && x > 0) (a != d || x != 5) !(true && false) (x > y || a == 'A' || d != 'A')

all 4 conditions are true Only Condition 2 is true Condition 2 and Condition 4 are true only Conditions 2, 3,4 are all true, Conditions 1 is not all 4 conditions are false

11. Which of the following are true about check boxes? a. b. c. d. e.

ANS: E 12. Every iterator a. b. c. d. e.

has a hasNext() method has a hasFirst()method has a hasNextInt()method has a isEmpty()method None of these

2 64 100 128 None of these; this is an infinite loop

15. How many times will the following loop iterate? int x = 10; while (x > 0) { System.out.println(x); x--; } a. b. c. d. e.

0 once 9 times 10 times 11 times

0 2 3 4 5

ANS: C

Since a > 0 is true, the next condition is checked. Since b < 0 is false, the else clause for this condition is executed. Since a > 5 is false the else clause for this condition is executed, which is x = x + 3. Therefore, 3 is added to x, so it is now 3. 18. Refer to Code Segment Ch 05-1. If x is currently 0, a = 0 and b = -5, what will x become after the statement shown is executed? a. b. c. d. e.

0 2 3 4 5

ANS: E Since a > 0 is true, the if clause for this condition is executed which is another if statement. Its condition, b < 0 is true so its if clause is executed which is x = x + 5, so now x is 5.

if (score < 60) grade = 'F'; ANS: if (score >= 90) grade = 'A'; else if (score >= 80) grade = 'B'; else if (score >= 70) grade = 'C'; else if (score >= 60) grade = 'D'; else grade = 'F'; 2. A truth table shows, for the various true or false values of boolean variables, what the result of a boolean condition is. Fill in the following truth table. Assume that a, b and c are boolean variables. a false false false false true true true true

b false false true true false false true true

c false true false true false true false true

a && (!b

|| c)

b false false true true false false true true

c false true false true false true false true

a && (!b false false false false true true false true

|| c)

ANS: a false false false false true true true true

b false false true true false false true true

c false true false true false true false true

!(a && b) ||

!(a && c)

b false false true

c false true false

!(a && b) ||

!(a && c)

ANS: a false false false

true true true

false true true true true

true false false true true

true false true false true

true true true true false

}

Java Software Solutions, 9e (Lewis/Loftus) Chapter 6 More Conditionals and Loops TRUE/FALSE 1. A switch statement must have a default clause. ANS: F The default clause is optional. 2. Each switch statement must terminate with a break statement. ANS: F They often do but if the break statement is not present, the flow of control continues into the next case. 3. Control in a switch statement jumps to the first matching case. ANS: T The switch expression is evaluated and control jumps to the first matching case, then continues from there. 4. The following for loop is an infinite loop:: for(int j = 0; j < 1000;) i++; ANS: T This loop initializes j to 0 and compares it to 1000, but does not alter j after each loop iteration. In reality, the loop will terminate with a run-time error eventually once i becomes too large to store in memory, but logically, this is an infinite loop. 5. It is possible to convert any type of loop (while, do, for) into any other. ANS: T All loop statements have equivalent expressive power. 6. The following loop is syntactically valid: for(int j = 0; j < 1000; j++) j--; ANS: T The Java compiler does not care that you are incrementing j in the loop but decrementing j in the loop body. Logically, this loop makes no sense because j will continuously be incremented and decremented so that it never reaches 1000, but there is nothing wrong with the loop syntactically.

7. In Java, it is possible to create an infinite loop out of while and do loops but not for loops. ANS: F

It is true that while and do loops can be infinite loops, but it is also true that Java for loops can be infinite loops. This is not true in some other programming languages where for loops have a set starting and ending point, but Java for loops are far more flexible than most other language's for loops. 8. A conditional operator is virtually the same as a switch statement. ANS: F The conditional operator is more like an if-else statement. 9. A for statement is normally used when you do not know how many times the loop should be executed. ANS: F A for statement is normally used when you do know how many times the loop should be executed. 10. A loop can be used in a GUI to draw concentric circles. ANS: T MULTIPLE CHOICE 1. You might choose to use a switch statement instead of nested if-else statements if a. the variable being tested might equal one of several hundred integer values b. the variable being tested might equal one of a few integer values c. there are two or more integer variables being tested, each one of which could be one of several hundred values d. there are two or more integer variables being tested, each one of which could be one of a few values e. None of these; you would never choose a switch statement instead of nested if-else statements under any circumstances. ANS: B The switch statement can only be used if there is a single variable being tested and it is an integer type (an int or a char in Java). Further, because you have to enumerate each possible value being tested, the switch statement only makes sense if the number of values being tested is a small number. 2. If a switch statement contains no break statements at all, a. a syntax error will occur b. each of the case clauses will be executed every time the switch statement is encountered

c. this is equivalent to having the switch statement always take the default clause, if one is present d. this is not a syntax error but nothing within the switch statement will ever be executed e. None of these ANS: E Although writing such a switch statement is unusual, it is entirely legal. The normal rules for the switch statement execution apply. The matching case clause being executed after the switch statement is evaluated and, following that, all subsequent clauses are executed, in order, since there are no break statements to terminate execution. 3. A continue statement a. b. c. d. e.

may be used within a while or a do-while loop but not a for loop is identical to a break statement within Java loops may be used within any Java loop statement may be used within a for loop but not within a while or a do-while loop None of these

ANS: C Although use of continue statements should be avoided, if possible, they may be used within any of Java's three types of loops. 4. How can the following statement be rewritten using a conditional operator? if(x <0) y = x; else y = 0; a. b. c. d. e.

y = (x < 0) ? x : 0; x = (x < 0) ? y : 0; (x < 0) ? y = x : y = 0; y = (x < 0); y = if(x < 0) x : 0;

ANS: A The conditional operator of Java tests a condition, (x < 0) in this case, and if true, returns the value after the ? (x in this case) and if false, returns the value after the : (0) in this case). The original if statement is to assign y to x if (x < 0) and 0 otherwise. This will be accomplished by assigning y to be x or 0 based on (x < 0), as shown in A. In B, x is assigned the value of y or 0 which is backward. In C, the conditional operator is syntactically invalid. In D, y would be set to either true or false depending on (x < 0), and the statement in E is syntactically invalid. 5. Given the following code, where x = 0, what is the resulting value of x after the for loop terminates? for(int i = 0; i < 5; i++) x += i; a. b. c. d. e.

0 4 5 10 15

ANS: D Each pass through the for loop results with the current value of the loop index, i, being added to x. The first time through the loop, i = 0 so x = x + 0 = 0. The second time through the loop i = 1 so x = x + 1 = 1. The third time through the loop i = 2 so x = x + 2 = 3. The fourth time through the loop i = 3 so x = x + 3 = 6. The fifth and final time through the loop i = 4 so x = x + 4 = 10. 6. The do loop differs from the while loop in that a. the while loop will always execute the body of the loop at least once b. the do loop will always execute the body of the loop at least once c. the do loop will continue to loop while the condition in its while statement is false and the while loop will continue to loop while the condition in its while statement is true d. the while loop will continue to loop while the condition in its while statement is false and the do loop will continue to loop while the condition in its while statement is true e. None of these; there is no difference between the two types of loops ANS: B Because the do loop does not test the condition until after the body of the loop executes, the body will always execute at least one time, but the while loop tests the condition first, and so if the condition is false the first time, the body does not execute even one time. 7. How many times will the following loop iterate? int x = 10; do { System.out.println(x); x--; } while(x > 0); a. b. c. d. e.

0 times 1 time 9 times 10 times 11 times

ANS: E The variable x starts at 10. Each pass through the loop, x is decremented and the loop finally exits once x is no longer greater than 0, which in this case means once x becomes 0. So the loop body executes for x = 10, x = 9, x = 8, and so forth down to x = 0. This is 11 times.

8. How many times will the following nested loop structure execute the innermost statement (x++;)? for(int j = 0; j < 100; j++) for(int k = 100; k > 0; k--) x++; a. b. c. d.

100 200 10,000 20,100

e. 1,000,000 ANS: C The outer loop iterates 100 times. Each time it iterates, the inner loop, and the x++; statement, execute 100 times. Therefore, the statement x++; executes 100*100 = 10,000 times. 9. Given that s is a String, what does the following loop do? for(int j = s.length(); j > 0; j--) System.out.print(s.charAt(j-1); a. b. c. d. e.

It prints s out backwards It prints s out forwards It prints s out backwards after skipping the last character It prints s out backwards but does not print the first character It yields a run-time error because there is no character at s.charAt(j-1) for j = 0

ANS: A The variable j counts down from the length of the String to 1, each time printing out the character at position j-1. The character at length-1 is the first character printed and this is the last character of the String. It continues until it reaches j = 1, and prints out the character at position j-1, or the 0th character, so it prints the entire String backwards. 10. What does the break statement do? a. It ends a program. b. It transfers control out of the current control structure such as a loop or switch statement. c. It ends the current line of output, returning the cursor. d. It denotes the end of a switch statement. e. It indicates the end of a line when using System.out.print. ANS: B This is the exit statement that allows the programmer to exit a control structure from inside of that control structure. 11. If a break occurs within the innermost loop of a nested loop that is three levels deep, a. just the innermost loop will be "broken" b. all loops are "broken" and execution continues from after the end of the loop c. all but the outermost loops are "broken" and execution continues from the next iteration of the outermost loop d. a syntax error is generated unless there are break or continue statements at each loop level e. None of these are true ANS: A The innermost loop is broken, and execution continues from just after the end of that loop. 12. Which of the following statements are true about Java loops? a. All three loop types are functionally equivalent. b. while loops and do loops are essentially the same, but while loops always execute at least once.

c. If you know the number of times that a loop is to be performed, the best type of loop to use is a while loop. d. Loops may be replaced by an appropriate combination of if-else and switch statements. e. None of these ANS: A In Java, as in most languages, the looping statements are all essentially equivalent (and almost interchangeable). Their principal difference(s) relate to when the controlling condition is evaluated and whether there is syntax for incrementation/update. 13. How many times will the System.out.println("*"); statement execute inside of the following nested for loops? for(j = 0; j < 10; j++) for(k = 10; k > j; k--) System.out.println("*"); a. b. c. d. e.

50 100 55 10 20

ANS: C The first iteration of the outer loop has j = 0, so the inner loop iterates from 10 down to 1, or 10 times. The next iteration of the outer loop has j = 1, so the inner loop iterates from 10 down to 2, or 9 times. This continues until the outer loop has j = 9, in which case the inner loop iterates for k = 10 only, or 1 time. Thus, the System.out.println("*"); statement executes a total of 10 + 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1 = 55 times. 14. Which of the following would rotate an Ellipse named lipse 30 degrees counterclockwise? a. b. c. d. e.

lipse.setRotate(30); lipse.setRotate(370); lipse.setRotate(-30); Ellipse.lipse.setRotate(30); Ellipse.lipse.setRotate(-10*3);

ANS: C Code Example Ch 06-1 In the following example, x is an int: switch (x) { case 3 : x += 1; case 4 : x += 2; case 5 : x += 3; case 6 : x++; case 7 : x += 2; case 8 : x--; case 9 : x++ }

15. Refer to Code Example Ch 06-1: If x is equal to 5, what will the value of x be after the switch statement executes? a. b. c. d. e.

8 6 11 5 10

ANS: C Since there are no break statements, the flow falls through any cases following the one that is true. The first case to be true is 5 since x is 5 prior to the switch statement. This changes x to 8, then to 9, then to 11, then to 10, and then finally back to 11. 16. Refer to Code Example Ch 06-1: If x is equal to 3, what will the value of x be after the switch statement executes? a. b. c. d. e.

5 6 11 10 12

ANS: E Since there are no break statements, the flow falls through any cases following the one that is true. The first case to be true is 3 since x is 3 prior to the switch statement. This changes x to 4, then to 6, then to 9, then to 10, then to 12, then to 11, and then finally back to 12. PROBLEM 1. Rewrite the following nested if-else statements using an equivalent switch statement. if (letter == 'A' || letter == 'a') System.out.println("Excellent"); else if (letter == 'B' || letter == 'b') System.out.println("You can do better"); else if (letter == 'C' || letter == 'c') System.out.println("Try harder"); else if (letter == 'D' || letter == 'd') System.out.println("Try much harder"); else System.out.println("Try another major! "); ANS: switch (letter) { case 'A', 'a' : System.out.println("Excellent"); break; case 'B', 'b' : System.out.println("You can do better"); break; case 'C', 'c' : System.out.println("Try harder"); break; case 'D', 'd' : System.out.println("Try much harder"); break; default : System.out.println("Try another major! "); }

2. Given the following tax table information, write Java code to assign the double taxRate appropriately, given the double pay. Select the selection statement (if, if-else, switch) that makes the most sense. If pay is more than 100,000, tax rate is 40% If pay is more than 60,000 and less than or equal to 100,000, tax rate is 30% If pay is more than 30,000 and less than or equal to 60,000, tax rate is 20% If pay is more than 15,000 and less than or equal to 30,000, tax rate is 10% If pay is more than 5,000 and less than or equal to 15,000, tax rate is 5% If pay is less than or equal to 5,000, tax rate is 0% ANS: Use a nested if-else structure as it requires the least amount of code. A switch statement is not possible because pay is a double and the switch statement can only be used for int types. if (pay > 100000) taxRate = 0.40; else if (pay > 60000) taxRate = 0.30; else if (pay > 30000) taxRate = 0.20; else if (pay > 15000) taxRate = 0.10; else if (pay > 5000) taxRate = 0.05; else taxRate = 0.0; 3. Write a declaration that initializes an int variable named num1 to 100 if the boolean variable score is true and to 50 otherwise, using the conditional operator. ANS: int num1 = (score) ? 100 : 50; 4. Rewrite the following if-else statement using a conditional operator. if (x > y) z = x; else z = y; ANS: z = (x > y) ? x : y; 5. Write a do loop to obtain a list of scores from a teacher. The teacher should end input by entering the sentinel value, 999. The program should output the average of the scores. ANS: Scanner scan = new Scanner(System.in); int score, count, sum = 0; do { sum += score; System.out.print("Enter a score or 999 to quit): "); score = scan.nextInt();

count++; } while (score != 999) average = sum / (count - 1); System.out.println(average); 6. Describe a situation where you should use a do loop and a situation where you should use a while loop. ANS: The do loop is used if you want to execute the loop body at least one time. This is useful for data verification (asking the user for a value, and only if the user has entered an improper value does your code repeat and try again). A while loop does not necessarily execute if the loop condition is not initially true. This might be useful if you want to control entrance to a loop such as only trying to sum up a list of values if the user actually has values to sum up. 7. The following for loop is odd in that the loop increment value changes during iterations of the loop. Determine the number of times the loop iterates and the final value of j after the loop terminates. int k = 0; for (j = 0; j < 20; j += k) k++; ANS: Six times with j = 21. Explanation: The first iteration has j = 0, k is then incremented in the loop body to 1 and j is incremented after the loop body executes to be j + k = 0 + 1 = 1. For the second iteration, k is incremented to 2 and j is incremented to j + k = 1 + 2 = 3. For the third iteration, k is incremented to 3 and j is incremented to 3 + 3 = 6. For the fourth iteration, k is incremented to 4 and j is incremented to 6 + 4 = 10. For the fifth iteration, k is incremented to 5 and j is incremented to 10 + 5 = 15. For the sixth iteration, k is incremented to 6 and j is incremented to 15 + 6 = 21. Now, since (j < 20) is no longer true, the loop terminates. 8. Write code that outputs all of the int values between 1 and 100 with five values per line, and each of those five values spaced out equally. Use a single for loop to solve this problem. ANS: for (int j = 1; j <= 100; j++) { System.out.print(j + "\t"); if (j % 5 == 0) System.out.println( ); } 9. Write the code to display an ImageView named the_view at half its original size. ANS: the_view.setScaleX(0.5); the_view.setScaleY(0.5);

7. In Java, it is possible to create an infinite loop out of while and do loops but not for loops. ANS: F

y = (x < 0) ? x : 0; x = (x < 0) ? y : 0; (x < 0) ? y = x : y = 0; y = (x < 0); y = if(x < 0) x : 0;

0 4 5 10 15

ANS: D

Each pass through the for loop results with the current value of the loop index, i, being added to x. The first time through the loop, i = 0 so x = x + 0 = 0. The second time through the loop i = 1 so x = x + 1 = 1. The third time through the loop i = 2 so x = x + 2 = 3. The fourth time through the loop i = 3 so x = x + 3 = 6. The fifth and final time through the loop i = 4 so x = x + 4 = 10. 6. The do loop differs from the while loop in that a. the while loop will always execute the body of the loop at least once b. the do loop will always execute the body of the loop at least once c. the do loop will continue to loop while the condition in its while statement is false and the while loop will continue to loop while the condition in its while statement is true d. the while loop will continue to loop while the condition in its while statement is false and the do loop will continue to loop while the condition in its while statement is true e. None of these; there is no difference between the two types of loops ANS: B Because the do loop does not test the condition until after the body of the loop executes, the body will always execute at least one time, but the while loop tests the condition first, and so if the condition is false the first time, the body does not execute even one time. 7. How many times will the following loop iterate? int x = 10; do { System.out.println(x); x--; } while(x > 0); a. b. c. d. e.

0 times 1 time 9 times 10 times 11 times

8. How many times will the following nested loop structure execute the innermost statement (x++;)? for(int j = 0; j < 100; j++) for(int k = 100; k > 0; k--) x++; a. b. c. d. e.

100 200 10,000 20,100 1,000,000

ANS: C The outer loop iterates 100 times. Each time it iterates, the inner loop, and the x++; statement, execute 100 times. Therefore, the statement x++; executes 100*100 = 10,000 times. 9. Given that s is a String, what does the following loop do? for(int j = s.length(); j > 0; j--) System.out.print(s.charAt(j-1); a. b. c. d. e.

d. Loops may be replaced by an appropriate combination of if-else and switch statements. e. None of these ANS: A In Java, as in most languages, the looping statements are all essentially equivalent (and almost interchangeable). Their principal difference(s) relate to when the controlling condition is evaluated and whether there is syntax for incrementation/update. 13. How many times will the System.out.println("*"); statement execute inside of the following nested for loops? for(j = 0; j < 10; j++) for(k = 10; k > j; k--) System.out.println("*"); a. b. c. d. e.

50 100 55 10 20

lipse.setRotate(30); lipse.setRotate(370); lipse.setRotate(-30); Ellipse.lipse.setRotate(30); Ellipse.lipse.setRotate(-10*3);

ANS: C Code Example Ch 06-1 In the following example, x is an int: switch (x) { case 3 : x += 1; case 4 : x += 2; case 5 : x += 3; case 6 : x++; case 7 : x += 2; case 8 : x--; case 9 : x++ }

15. Refer to Code Example Ch 06-1: If x is equal to 5, what will the value of x be after the switch statement executes? a. b. c. d. e.

8 6 11 5 10

5 6 11 10 12

Java Software Solutions, 9e (Lewis/Loftus) Chapter 7 Object-Oriented Design TRUE/FALSE 1. The most important decisions regarding the development of a system are made during the implementation phase while code is actively being written. ANS: F All of the important decisions should be made during earlier phases of development, particularly during the design phase. By the time the implementation phase is reached, the entire system design should be available and this phase should only entail translating the design into code. 2. Unlike the String class where you must pass a message to an object (instance) of the class, in order to use the Math class, you pass messages directly to the class name, as in Math.sqrt(). ANS: T The Math class uses methods known as static methods (or class methods) which are invoked by passing a message directly to the class name itself rather than to an object of the class. 3. Assume that the class Bird has a static method fly(). If b is a Bird, then to invoke fly, you could do Bird.fly();. ANS: T Static methods are invoked through the class and not an object of the class. This is because the static method is shared among all instances. So, Bird.fly(); will invoke fly. It should be noted that fly can also be invoked through b, so b.fly(); will also work. 4. Interface classes cannot be extended but classes that implement interfaces can be extended. ANS: F Any class can be extended whether it is an interface, implements an interface, or neither. The only exception to this is if the class is explicitly modified with the word final in which case it cannot be extended. 5. If classes C1 and C2 both implement an interface Cint, which has a method, whichIsIt, and if C1 c = new C1(); is performed at one point of the program, then a later instruction c.whichIsIt(); will invoke the whichIsIt method defined in C1. ANS: F Because C1 and C2 implement the same interface, they both implement whichIsIt. The variable c is known as a polymorphic variable, meaning that it can change from being an C1 to a C2. So, the message c.whichIsIt(); may invoke C1's whichIsIt or C2's whichIsIt. There is no way to tell until runtime. 6. Any class can implement an interface, but no classes can implement more than a single interface.

ANS: F Classes can implement any number of interfaces, 0, 1, or more. 7. All objects implement Comparable. ANS: F Comparable is an interface, and the class must define the CompareTo method and explicitly state that it implements Comparable to be considered an implementation of Comparable. Most classes do not implement Comparable. 8. Formal parameters are those that appear in the method call and actual parameters are those that appear in the method header. ANS: F The question has the two definitions reversed. Formal parameters are those that appear in the method header, actual parameters are the parameters in the method call (those being passed to the method). 9. It is not possible to test out any single method or class of a system until the entire system has been developed, and so all testing is postponed until after the implementation phase. ANS: F While it is true that testing occurs after implementation, some testing can take place during implementation. In Java, it is possible to test out single methods or classes by creating stubs of other methods and classes that are simple placeholders. For instance, if one method calls another method and the second method is not yet written, a stub of the second method can be written that simply returns a value that would normally be expected so that the first method can be tested. 10. In black-box testing, the tester should already know something about how the program is implemented so that he/she can more carefully identify what portion(s) of the software may lead to errors. ANS: F In black-box testing, the tester should know nothing about how the software is implemented. In essence, the software is a black-box which has an input and an output and the mechanisms of the program are opaque. If the tester does know something about how the program works, then the tester's test cases might be biased. If the tester knows how the program works, then testing is known as glass-box testing. 11. The versions of an overloaded method are distinguished by the number, type, and order of their parameters. ANS: T 12. The graphical effect caused when a shape seems to resize as the mouse is dragged is known as rubberbanding.

ANS: T MULTIPLE CHOICE 1. During program development, software requirements specify a. b. c. d. e.

how the program will accomplish the task what task the program must perform how to divide the task into subtasks how to test the program when it is done All of these

ANS: B The specification phase is to understand the problem at hand so that the programmer can determine what needs to be done to solve the problem. The other efforts listed above are part of the design phase (A, C) and testing phase (D). 2. Once we have implemented the solution, we are not done with the problem because a. b. c. d.

the solution may not be the best or most efficient the solution may have errors and need testing and fixing before we are done the solution may, at a later date, need revising to handle new specifications the solution may, at a later date, need revising because of new programming language features e. All of these ANS: E A program should not be considered as a finished product until we are reasonably assured that it is efficient and error-free. Further, it is common that programs require modification in the future because of a change to specifications or a change to the language or computer running the program. 3. Of the various phases in software development, which of the following is usually the lengthiest? a. b. c. d. e.

specification design implementation testing maintenance

ANS: E The maintenance phase exists for as long as the software is in use. Software requires modification (such as new requirements like new features or I/O specifications) and so the maintenance phase is ongoing whereas the other phases end once the software has been released and is in use. 4. The activities of the development cycle are generally thought to a. b. c. d. e.

be strictly linear be rigidly ordered overlap have optional steps both A and B are true

ANS: C Phases often need revisiting resulting in a development cycle where the development activities overlap. 5. The idea of having programmers and developers meet in order to critique a software design or implementation is known as a. b. c. d. e.

an interview a walkthrough prototyping aggregation evolutionary development

ANS: B Such meetings are very useful so that the various members can analyze the solution to that point in time and offer suggestions to enhance the design and implementation. This is called a walkthrough because it involves going step-by-step through the proposed or implemented design. 6. Modifying a program in order to eliminate deficiencies is done in the __________ phase of the development cycle. a. b. c. d. e.

design implementation testing use maintenance

ANS: B While testing is used to find errors, deficiencies are more commonly identified by the users of the system once the system has been released. After such deficiencies have been identified, it is up to the software maintenance group to eliminate them in future versions of the software. 7. It is easier to correct errors found in a program if a. b. c. d. e.

they are identified early in the development cycle they are identified during testing they are identified during program use they are identified during maintenance All of the above are equally true; errors are easily corrected at any of these stages

ANS: A Errors introduced early in the development cycle often cause tremendous problems if not caught early on. Therefore, errors found in testing, use or maintenance phases may be too embedded in the systems' design to be easily corrected. But if found early on, the errors can be completely eliminated. 8. In general, spending more time in development to ensure better software will a. b. c. d. e.

shorten testing time slightly reduce maintenance efforts slightly increase maintenance efforts greatly reduce maintenance efforts not alter the time it takes for any other stage

ANS: D Spending more time in development promises better software, which in turn leads to less maintenance effort. 9. It is important to dissect a problem into manageable pieces before trying to solve the problem because a. most problems are too complex to be solved as a single, large activity b. most problems are solved by multiple people and it is easy to assign each piece to a separate person c. it is easier to integrate small pieces of a program into one program than it is to integrate one big chunk of code into one program d. the first solution may not solve the problem correctly e. all of these ANS: A Any interesting problem will be too complex to solve easily as a single activity. By decomposing the problem, we can build small solutions to each piece and then integrate the pieces. Answer D is true, but is not the reason why we break a problem down into pieces. 10. The goal of testing is to a. b. c. d. e.

ensure that the software has no errors find syntax errors find logical and run-time errors evaluate how well the software meets the original requirements give out-of-work programmers something to do

ANS: C Testing is required because all software will have errors. Complex systems especially need testing before they can be released. The types of errors sought are logical errors and run-time errors. All syntax errors will have been identified and fixed during implementation. 11. In which phase of program development would you expect the programmer(s) to create the pseudocode? a. b. c. d. e.

software requirements software design software implementation software testing this could occur at any time

ANS: B Pseudocode is a description of an algorithm written in an English-like way rather than in a specific programming language. This is part of the program's design. In the implementation phase, the programmer(s) translate(s) the pseudocode into the programming language being used. 12. In which phase of program development would you expect the programmer(s) to determine the classes and objects needed? a. software requirements b. software design c. software implementation

d. software testing e. this could occur at any time ANS: B Determining which classes and objects to use or create is part of the design. 13. If a programmer follows the four phases of program development as intended, which of the four phases should require the least amount of creativity? a. b. c. d. e.

software requirements software design software implementation software testing all four levels require equal creativity

ANS: C Once the implementation phase has been reached, the algorithm should have already been specified, so the only effort involved in the implementation phase is of translating from the design (which is probably in an English-like pseudocode) to the programming language, and entering the code through an editor. The requirements and design phases require understanding the problem and coming up with a solution respectively, requiring creativity, and the testing phase will require diagnostic abilities usually forcing the programmer(s) to be creative in how the errors are found and fixed. 14. Having multiple class methods of the same name where each method has a different number of or type of parameters is known as a. b. c. d. e.

encapsulation information hiding tokenizing importing method overloading

a recipe a computer program pseudocode a shopping list travel directions

ANS: D An algorithm is a step-by-step description of how to solve a problem, written at some level of specificity. The recipe and probably the pseudocode are written at a "high level" whereas a program and perhaps travel directions are written in more detail. A shopping list is not a step-by-step description, so it would not qualify as an algorithm. 16. In order to create a constant, you would use which of the following Java words? a. private b. static

c. int d. final e. class ANS: D The reserved word final indicates that this is the final value that will be stored in this variable, thus making it unchangeable, or constant. While constants can be of type int, constants can be of any other type as well. It is the final reserved word that makes the value unchangeable.

17. Which of the following methods is a static method? The class in which the method is defined is given inside the parentheses following the method name. a. b. c. d. e.

equals(String) toUpperCase(String) sqrt(Math) format(DecimalFormat) None of these

ANS: C The Math class defines all of its methods to be static. Invoking Math methods is done by using Math rather than a variable of type Math. The other methods above are not static. 18. In order to implement Comparable in a class, what method(s) must be defined in that class? a. b. c. d. e.

equals compares both lessThan and greaterThan compareTo both compares and equals

ANS: D The Comparable class requires the definition of a compareTo method that will compare two objects and determine if one is equal to the other, or if one is less than or greater than the other and respond with a negative int, 0 or a positive int. Since compareTo responds with 0 if the two objects are equal, there is no need to also define an equals method. 19. Static methods cannot a. b. c. d. e.

reference instance data reference non-static instance data reference other objects invoke other static methods invoke other non-static methods

ANS: B A static method is a method that is part of the class itself, not an instantiated object, and therefore the static method is shared among all instantiated objects of the class. Since the static method is shared, it cannot access non-static instance data because all non-static instance data are specific to instantiated objects. A static method can access static instance data because, like the method, the instance data is shared among all objects of the class. A static method can also access parameters passed to it. 20. An object that refers to part of itself within its own methods can use which of the following reserved words to denote this relationship?

a. b. c. d. e.

inner i private this static

ANS: D The reserved word this is used so that an object can refer to itself. For instance, if an object has an instance data x, then this.x refers to the object's value x. While this is not necessary, it can be useful if a local variable or parameter is named the same as an instance data. The reserved word this is also used to refer to the class as a whole, for instance, if the class is going to implement an interface class rather than import an implementation of an interface class. 21. An example of an aggregation relationship is a. b. c. d. e.

parent and child animal and dog teacher and computer phone and fax machine All of these

ANS: C An aggregate relationship describes how one object accomplishes a task by using another object. In the above list, the teacher uses the computer. The relationship in A is one of lineage (possibly ownership), the relationship in B is an "is-a" relationship as a dog is a child class of animal, and the relationship in D is one of similarity since phone and fax machine might be thought of as sibling classes, related to each other in that they are both children of a more general communication class. 22. Abstract methods are used when defining a. b. c. d. e.

interface classes derived classes classes that have no constructor arrays classes that have no methods

ANS: A An interface is a class that has defined some of its components, but leaves other components (methods) for you to implement. So, these components (methods) are referred to as abstract and defined in the interface class as abstract. Code Description Ch 07-1 Consider a class called ChessPiece. This class has two instance data, String type and int player. The variable type will store "King", "Queen", "Bishop", etc. and the int player will store 0 or 1 depending on whose piece it is. We wish to implement Comparable for the ChessPiece class. Assume that, the current ChessPiece is compared to a ChessPiece passed as a parameter. Pieces are ordered as follows: "Pawn" is a lesser piece to a "Knight" a "Bishop" and "Knight" are equivalent for this example both "Bishop" and "Knight" are lesser pieces to a "Rook"

a "Rook" is a lesser piece to a "Queen" a "Queen" is a lesser piece to a "King". 23. Refer to Code Description Ch 07-1: Which of the following method headers would properly define the method needed to make this class Comparable? (cp designates ChessPiece) a. b. c. d. e.

public boolean comparable(Object cp) public int comparable(Object cp) public int compareTo(Object cp) public int compareTo() public boolean compareTo(Object cp)

ANS: C To implementComparable, you must implement a method called compareTo which returns an int. Further, since this class will compare this ChessPiece to another, we would expect the other ChessPiece to be passed in as a parameter. 24. Refer to Code Description Ch 07-1: Which of the following pieces of logic could be used in the method that implements Comparable? Assume that ChessPiece has a method called returnType which returns the type of the given piece. a. b. c. d. e.

if (this.type < a.returnType()) return -1; if (this.type = = a.returnType()) return 0; if (this.type.equals(a.returnType()) return 0; if (a.returnType().equals("King")) return -1; if (a.returnType().equals("Pawn")) return 1;

ANS: C If the type of this piece and of a are the same type, then they are considered equal and the method should return 0 to indicate this. Note that this does not cover the case where this piece is a "Knight" and a is a "Bishop", so additional code would be required for the "equal to" case. The answer in B is not correct because it compares two Strings to see if they are the same String, not the same value. The logic in D and E are incorrect because neither of these takes into account what the current piece is, only what the parameter's type is. In D, if a is a "King", it will be greater than this piece if this piece is not a "King", but will be equal if this piece is a "King" and similarly in E, it does not consider if this piece is a "Pawn" or not. Finally, A would give a syntax error because two Strings cannot be compared using the < operator.

PROBLEM 1. Provide a reason why an instance data would be declared static. ANS: If an instance data is to be shared among all objects of the class, the instance data would be static. As an example, an instance data that counts the number of times something has happened across all objects of the class would be made static. If we are writing a chess game and have a ChessPiece class that includes a method called movePiece, we would want to know how many moves a player has made, but not necessarily how many times a single piece has been moved. So, all of the ChessPieces share a numberOfTimesMoved instance data that is incremented by any ChessPiece whenever it is moved.

2. Provide a reason why a method would be declared static. ANS: A method is declared static if it might be used, not by the current object, but by any objects of the class. That is, the method does not require access to any single object's instance data. Consider a class called Point that consists of an x and y coordinate. To determine the distance between two Points, we could make a static computeDistance method. It is passed two Points as parameters and computes the distance. 3. Explain the difference between implementing an interface and a derived class. ANS: Implementing an interface means that you are adding to your class any mechanisms defined in an abstract class. Your class essentially is expanded to contain those items defined in the interface class but you have to implement any of those items that are abstract. The appeal is that other objects might call upon your class to use the interface methods without knowing anything else about your class. The derived class is similar in that you are gaining items previously defined, although in this case, those items are defined in the parent class (as long as those items are protected or public) and you do not have to implement any of them unless you want to redefine them. One difference between the two is that the interface cannot be instantiated directly. Another difference is that your class "inherits" abstract methods from the interface class as opposed to implemented methods from a super class. 4. Define an interface class that contains two int constants, X = 5 and Y = 10 and one int method called useXY which receives no parameters. Call your interface class XYClass. ANS: public interface XYClass { public final int X = 5; public final int Y = 10; public int useXY(); } 5. Assume a class Foo implements Comparable. Without knowing anything else about the Foo class, write an equals method that returns true if the Foo parameter passed to this Foo is equal to this Foo as determined by using the implementation of Comparable. ANS: public boolean equals(Foo a) { if(compareTo(a)) = = 0) return true; else return false;

} Code Description Ch 07-1 Consider a class called ChessPiece. This class has two instance data, String type and int player. The variable type will store "King", "Queen", "Bishop", etc. and the int player will store 0 or 1 depending on whose piece it is. We wish to implement Comparable for the ChessPiece class. Assume that, the current ChessPiece is compared to a ChessPiece passed as a parameter. Pieces are ordered as follows: "Pawn" is a lesser piece to a "Knight" a "Bishop" and "Knight" are equivalent for this example both "Bishop" and "Knight" are lesser pieces to a "Rook" a "Rook" is a lesser piece to a "Queen" a "Queen" is a lesser piece to a "King". 6. Refer to Code Description Ch 07-1: To implement Comparable for the ChessPiece class, the current ChessPiece's type is compared to a ChessPiece passed as a parameter. The method should return 0 if the types are equal, -1 if this piece's type is a lesser piece than the parameter's type, and 1 if this piece's type is a greater piece than the parameter's type. Create this code. ANS: public int compareTo(ChessPiece a) { if (this.type.equals(a.returnType())|| (this.type.equals("Knight")&&a.returnType().equals("Bishop")) ||(this.type.equals("Bishop")&&a.returnType().equals("Knight"))) return 0; else if (this.type.equals("King")) return 1; else if (a.returnType().equals("King")) return-1; else if (this.type.equals("Queen")) return 1; else if (a.returnType().equals("Queen")) return -1; else if (this.type.equals("Rook")) return 1; else if (a.returnType().equals("Rook")) return -1; else if (this.type.equals("Knight")||(this.type.equals("Bishop")) return 1; else if (a.returnType().equals("Knight")||(a.returnType().equals("Bishop")) return -1; } 7. Refer to Code Description Ch 07-1: Write a static method that is passed two ChessPieces and determines if the two pieces are owned by the same player. It should return true or false.

ANS: public static boolean samePlayer(ChessPiece p1, ChessPiece p2) { return (p1.returnPlayer( ) = = p2.returnPlayer( )); } 8. In what way is black-box testing better than glass-box testing? In what way is glass-box testing better than black-box testing? ANS: Black-box testing is superior because the tester knows nothing of the software and so will test the software without preconceived ideas of where errors might exist. The tester is testing the software blindly, much as a user will use the software–without intimate knowledge of how the software works. The result should be that if errors exist that a user might stumble across, the tester should find them. While black-box testing of software has the advantage that the tester operates much like the users are expected to, the disadvantage is that it is a blind test, but there are times when knowledge of how the software functions could be useful. If programmers suspect that some awkward or difficult implementation may be buggy, then spending more time testing that portion of the software is advantageous. This form of testing requires knowledge of how the software works. So, both blackbox and glass-box testing have their own advantages and disadvantages. 9. Write code that outputs all of the int values between 1 and 100 with five values per line, and each of those five values spaced out equally. Use a single for loop to solve this problem. ANS: for (int j = 1; j <= 100; j++) { System.out.print(j + "\t"); if (j % 5 == 0) System.out.println( ); }