Stack
- Used to store variables inside a stack frame for each function
- Elements are added to the stalk as functions are called
- Memory is automatically deallocated (by the compiler) as the scope is exited
- Less space than the heap
- Faster creation and access time
- Generally the compiler knows how much space to assign for a stack frame
- Thread-safe
- A stack frame is only accessible by the owner thread
Interesting things to note
- Also known as the Call Stack
StackOverFlowError is thrown by the JVM when stack space runs out
Heap
- Used for Dynamic Memory Allocation
- More flexible memory management
- Useful for when the memory needs to remain allocated outside the scope
- Memory needs to be deallocated (manually or by a Garbage Collector)
- The heap memory is accessible by all threads (not thread-safe)
Interesting things to note
- Susceptible to memory leaks if memory is not deallocated properly
- Also called the heap-space
Differences
- In most languages the stack is fixed size, whereas the heap is able to resize
- Accessing a stack frame is easier than in the heap
- A stack frame is a smaller region of memory
- The Heap uses a hierarchical data-structure, compared to the Stack which is a Linear type structure (LIFO)
- The stack has a better locality of reference than the heap-space