Heap vs Stack

Memory areas in JVM

Interview Relevant: Fundamental concept
6 min read

Heap vs Stack

The JVM divides memory mainly into Heap and Stack, each serving a distinct purpose.

  • Heap: Stores objects, shared across threads
  • Stack: Stores method calls, local variables, thread-specific

Interview Tip: Stack memory is faster and automatically freed, heap memory is GC-managed.

Code Examples

Stack vs Heap allocation

java
1
2public void test() {
3    int x = 10;           // Stack
4    User u = new User();  // Reference in stack, object in heap
5}
6

Use Cases

  • Understanding performance
  • Debugging memory issues

Common Mistakes to Avoid

  • Assuming objects are stored on stack
  • Confusing reference vs object