MemoryAllocation in Java
Memory is a crucial resource for every programming language, but it is usually scarce, making it essential to thoroughly manage the memory without any leaks
Read:Why Java is better for web development
Memory allocation is the process of reserving a partial or entire portion of virtual or physical space This reserved virtual space is assigned to a program or process for execution through a process called memory management
To keep memory management lean, it is partitioned in ways that need less memory and helps the application program to run faster
Read:Java vs JavaScript: KnowThe Difference
In Java, memory is allocated in Java Virtual Machine (JVM) which is broadly divided into Stack Memory and Heap memory.
Java Stack Memory:An Overview
Java stack memory, also called temporary memory allocation, is the physical space allocated to each thread during run time It is a static memory allocation process where every primitive data value of a method, function calls, and heap memory object is stored. Stack memory can be accessed in the LIFO (Last In First Out) format
Read:Apache Beam Using Java
But, what does this LIFO mean? When a method is called, it creates (pushes) a new block on the top of stack memory to hold local values and references to other method objects And once the method ends, the block is cleared (popped) to be used in the next method
Put simply, Stack is the area that stores temporary variables that a function creates In stack memory, all the variables are stored, declared, and initialized at the runtime, i e, the memory will be automatically cleared.
Read: Top 5 Best Free Java Development IDE
Stack memory allocation takes place on a contiguous memory block The compiler determines the amount of memory that each type of variable in the program will need before allocation. A programmer doesn’t have to worry about the allocation and deallocation of Stack memory
The size of stack memory is restricted and if the program or process consumes more memory than the stack size, it will create a stack overflow leading to the failure of the program. To avoid stack overflow, you need to write a base condition for a program’s recursive call
Different Stack Operations: push(), pop(), isEmpty(), size(), isFull(), and top().
Pros and Cons of Java Stack
With a better understanding of Java Stack, you must also know its pros and cons
Read: Java For Data Science: What, Why, and When
Pros of Java Stack Memory:
● Stacks automatically expand and shrink with each new method being called and returned respectively
● It automatically allocates and deallocates memory to objects.
● Stack variables exist as long as the main method is being executed
● It has fast memory access.
● The stack doesn’t need synchronization and is thread safe as every thread operates in a stack of its own
Cons of Stack Memory in Java:
● You need to define the stack size before execution, making it limited to that size only
● In case the objects created exceed the defined size, it will lead to stack overflow.
● You cannot access methods randomly
● Stack falling outside the memory can cause abnormal or early termination of the program.
Heap Memory in Java
Heap memory is the part of JVM allocated memory shared by multiple threads in the application. It is used by Java runtime for allocating memory to JRE classes and objects. It provides a pile of space for developers to allocate and deallocate, hence, is called Heap
Read: Using Proxies with Java Web Scraping
NOTE: Heap memory has nothing to do with the heap data structure
The objects created in the Java program get stored in the Heap space, while the referencing information is stored in the Stack memory.
Heap memory allocation is further partitioned into three categories, namely, Young Gen, Old or Tenured Gen, and Permanent Gen, that help in prioritizing the Objects to be stored in the Heap space or Garbage collection
Read: BestTech Stack for WebApp Development
Heap memory is used by the application as long as it runs and does not follow any order like Stack. In Heap space, the memory blocks are handled dynamically as the Java Garbage Collector deletes or terminates the objects not being used. It throws java.lang.OutOfMemoryError, if the space of Heap memory gets full Unlike Stack memory, Heap objects can be accessed from anywhere in the application as they have global access
Pros and Cons of Java Heap
As we know what Heap Memory or Space is, let’s understand the pros and cons of using Java Heap memory
Pros of Heap Memory in Java:
● Heap memory is not static, hence can expand or shrink according to the program requirements.
● It provides global access to the created objects, making them accessible from anywhere in the application
● Not following LIFO, FIFO, etc., Heap memory allows random access.
● Can be used in Priority Queue
Cons of Heap Memory in Java:
● Heap is prone to memory leaks
● It has a much slower object access time as compared to stack memory, making it unavailable for other processes.
● Heap memory uses complex memory management techniques for the allocation and deallocation of memory.
● Heap memory requires Garbage collection to free up space as it is not done automatically
Heap v/s Stack Memory: Key Differences
Although we now know what heap and stack memory in Java is, it’s time to do a head-to-head comparison to help you easily compare the key differences both of them have
Parameter
Stack Memory
Heap Memory
Memory Size It has a smaller memory size It has a larger memory size
Usage Stack memory is used to execute threads while storing method calls, their reference, and primitive data
Heap space stores dynamically allocated JRE classes and objects
Lifetime Stack memory stays as long as the current method is being executed, hence, has a short life
Memory Allocation and Deallocation
Safety
Efficiency
There is an automatic memory allocation when a new method is invoked while the memory is automatically deallocated with the recursion of the method
As stack memory can only be accessed by the thread owner, it becomes a safe data storage
Stack memory provides faster allocation, deallocation, and accessibility to memory blocks, making it more efficient
Heap memory can be accessed anytime during the execution of the application, and hence, has a longer lifetime
Programmers need to allocate memory manually with the creation of new objects, while the garbage collector clears memory by removing unused objects
As Heap memory is visible and accessible to all the threads, it is not the safest to store data
Heap memory has a comparatively slower allocation, deallocation, and accessibility to memory blocks, making it less efficient
Ordering
Follows the Last In First Out order Due to dynamic allocation, Heap memory does not follow a fixed order for memory block allocation and deallocation
Visibility
Access Speed
Space Management
Only visible to the owner thread
Visible to all threads in the application
Can be accessed quickly. It is slower to access compared to stack memory.
Slack memory is managed by the operating system so it will not become fragmented.
Resizing
Implementation
Error
Conclusion
Heap memory can easily become fragmented as memory blocks are allocated first and freed according to their usage.
In stack, variables cannot be resized. In heap space, you can easily resize the variables.
You can implement Stack in one of three ways: using dynamic memory, array, and LinkedList.
It throws a stack overflow error
You can implement Heap memory in one of two ways: using trees or arrays.
It throws an out of memory error
So, that was all about stack and heap space in Java. We hope you found it helpful for your upcoming projects Concluding, JVM has two types of memory to make the application
execution more efficient All the method calls, references, and primitive type variables are stored in stack memory while all the dynamic objects get stored in the heap memory.
If you are an entrepreneur looking to develop a Java web application for your business, then get in touch with our experts who will gather your requirements and help you to hire developers who have years of experience and expertise in creating web apps best suited for your needs at an affordable cost.
So, what are you waiting for? Contact Us Now!
