What's the difference between StackOverflowError and OutOfMemoryError
Short answer:
OutOfMemoryError
is related to Heap.StackOverflowError
is related to stack
Long answer:
When you start JVM
you define how much RAM it can use for processing. JVM
divides this into certain memory locations for its processing purpose, two of those are Stack
& Heap
If you have large objects (or) referenced objects in memory, then you will see OutofMemoryError
. If you have strong references to objects, then GC can't clean the memory space allocated for that object. When JVM tries to allocate memory for new object and not enough space available it throws OutofMemoryError
because it can't allocate the required amount of memory.
How to avoid: Make sure un-necessary objects are available for GC
All your local variables and methods calls related data will be on the stack. For every method call, one stack frame will be created and local as well as method call related data will be placed inside the stack frame. Once method execution is completed, the stack frame will be removed. ONE WAY to reproduce this is, have an infinite loop for method call, you will see stackoverflow
error, because stack frame will be populated with method data for every call but it won't be freed (removed).
How to avoid: Make sure method calls are ending (not in an infinite loop)
Imagine you have a function like the following
public void f(int x) {
return f(x + 1);
}
When you'll call it the call will call f
again and again and again. At each call a bit of information is stored on the stack. Since the stack is limited in size you will get a StackOverflowError
.
Now imagine the following code:
for (int i = 1; i > 0; i++)
vector.add(new BigObject());
where BigObject
is a normal Java object. As you see, the loop never terminates. Each allocation is done on the heap thus it will be filled with BigObject
s and you will get an OutOfMemoryError
.
To recap:
OutOfMemoryError
is thrown when you are creating objectsStackOverflowError
is thrown when you are calling functions
StackOverflowError
happens when you execute too many methods one inside another (for example with an infinite recursion), which is limited by the size of the stack.
OutOfMemoryError
happens when the JVM runs out of space to allocate new objects, which are allocated on the heap.