Java Memory Management

Understanding how Java manages memory is crucial for writing efficient applications. Java memory is primarily divided into Stack and Heap.

Stack vs Heap

Feature	Stack Memory	Heap Memory
Storage	Local variables, method calls	Objects, instance variables
Access	Fast access	Slower access
Size	Small, fixed size	Large, dynamic size
Lifetime	Cleared when method execution ends	Cleared by Garbage Collector

Garbage Collection is the process of automatically identifying and discarding objects that are no longer in use to free up memory resources.

Mark: The GC identifies which pieces of memory are in use and which are not.
Sweep: The GC removes objects identified during the "mark" phase.
Compact: (Optional) Memory is compacted to prevent fragmentation.

Tip 💡

You can request garbage collection using System.gc(), but it is not guaranteed to run immediately.

Occurs when the stack memory is full, usually due to infinite recursion.

void recursive() {
    recursive(); // Infinite loop -> StackOverflowError
}

Occurs when the heap memory is full, usually due to creating too many objects or memory leaks.

List<String> list = new ArrayList<>();
while (true) {
    list.add("Memory Leak"); // Eventually -> OutOfMemoryError
}