Java Heap vs Stack: What’s the Difference?

Key Difference Between Java Heap vs Stack

Java virtual machine (JVM) allocates operating system memory to build Java heap objects and instances. Dynamic memory allocation and object creation occur on the heap in Java. Java garbage collects memory from the heap, which is at the bottom of the address space. Last-In-First-Out governs stack memory. Stack memory allocation is static. The heap memory is larger than the memory stack.

Java Heap vs Stack Comparison Table

Here’s a concise comparison of Java heap and stack in a table format:

Aspect	Java Heap	Java Stack
Purpose	Dynamic memory allocation for objects and data structures.	Stores method call frames and local variables.
Storage	Allocated on the heap memory, managed by the Java Virtual Machine (JVM).	Allocated on the stack memory, managed at runtime.
Lifetime	Objects in the heap exist for the duration of the program or until explicitly garbage-collected.	Method call frames and local variables exist for the duration of the method execution.
Memory Allocation Control	Managed by the JVM, allows dynamic allocation and deallocation of memory.	Managed automatically by the program’s execution flow.
Thread Safety	Objects in the heap can be shared among multiple threads, requiring synchronization.	Local variables on the stack are thread-safe as they are not shared.
Memory Usage Efficiency	Memory allocation and deallocation can be less efficient due to garbage collection overhead.	Memory allocation and deallocation are very efficient but limited in size.
Data Type	Used for objects and data structures such as arrays and custom classes.	Stores primitive data types and references to objects in the heap.
Dynamic Sizing	Heap size can be configured to grow dynamically based on JVM settings.	Stack size is typically fixed and defined at program startup.
Exception Handling	Handles exceptions using try-catch blocks and exceptions propagate up the call stack.	Handles exceptions using try-catch blocks and exceptions propagate up the call stack.
Recursion	Supports recursive method calls, but deep recursion may lead to stack overflow errors.	Supports recursive method calls, but limited stack size can lead to stack overflow errors.
Examples	Storing objects like instances of classes, arrays, and data structures.	Storing local variables, method parameters, and return addresses.