Difference Between Stack and Heap

Java or Japan Anti-Vivisection Association is a high-level object-oriented used for general purpose and cross-platform programming language.

In Java, memory management is managed automatically. It divides its memory into stack memory and heap memory.

Stack vs Heap 

The main difference between stack memory and heap memory is that the data structure of the stack is linear while the data structure of the heap is hierarchical. Allocation of stack memory is in a contiguous block. On the other hand, the allocation of heap memory is in random order. Variables of the stack cannot be resized, whereas variables of the heap can be resized. 

Stack vs Heap

The stack memory allocation takes place in the contiguous memory block. Programmers do not worry about memory to allocate stack variables and relocating them.

For global variables heap works as a buffer in which programming languages are saved. By default, in heap memory space, all globe variables are stored.

Comparison Table Between Stack and Heap 

Parameters of ComparisonStackHeap
InterpretationIn memory, it is a linear structure wherein sequentially the information is stored.In memory, there is dynamic allocation where all the data is randomly stored.
Memory allocationIn continuous blockIn random order
Speed FasterSlower
Data structureLinearNonlinear (hierarchical)
SizeFixedPossible to resize

What is Stack? 

In contemporary era computers, every thread has a region of memory that is reserved and called its stack. When the function executes, some of its local state data may add up to the top of the stack.

The stack is often beneficial to store variables local to the functions that are currently active. Programmers prefer a stack to store variable-length local data.

Stack memory mechanisms allow the memory of the system to work as temporary data storage and behave like a first-in-last-out buffer.  

Some of the advantages of the stack are automatic cleanup of the object, memory cannot be easily corrupted, and a big hand in allocation and deallocation of memory.

What is Heap? 

When programmers execute the instructions, then only heap memory is allocated. This kind of memory is called heap due to its availability of memory space in pile to allocate and de-allocate.

Heap memory allocation can be divided into:  

  1. Young generation- In this region of memory, all new objects or data allocate the space. In case, memory is filled Garbage collection helps to store the rest of the data.  
  2. Old or tenured generation- In this region older data objects are stored which are not often use or not at all.  
  3. Permanent generation- This region consists of JVM’s metadata for the application methods and runtime classes.  

There are several pros or benefits of using heap memory, such as variables can be accessed globally, no limit on memory size, the method used in the priority queue, and it runs garbage collection.

Main Differences Between Stack and Heap 

  1. Stack memory is helpful to store function calls and local variables. But heap memory is beneficial to store objects in Java.
  2. In stacks, stored variables are visible to the owner thread, or in Java, it is a kind of private memory. On the flip side, in heap objects which is created visible to all threads or among all threads the heap memory is shared. 
Difference Between Stack and Heap

Conclusion 

So, it can be concluded that both stack and heap are memory management platform which plays a vital role in Java. They both are chief memory areas but, they have different purposes.

Stack memory has the accessibility of high speed but only to local variables. On the flip side, heap memory accessibility speed has slower as compared to stack but allows access to variables globally.

References  

  1. https://arxiv.org/abs/1505.08075
  2. https://dl.acm.org/doi/abs/10.1145/1375634.1375655
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