Do Java primitives go on the Stack or the Heap?

java stack heap
Tom Brito picture Tom Brito · Sep 5, 2010 · Viewed 30.3k times · Source

I just know that the non-primitives (the objects) go on the heap, and methods go on the stack, but what about the primitive variables?

--update

Based on the answers, I could say the heap can have a new stack and heap for a given object? Given that the object will have primitive and reference variables..?

Answer

Jack Edmonds picture Jack Edmonds · Sep 5, 2010

Primitives defined locally would be on the stack. However if a primitive were defined as part of an instance of an object, that primitive would be on the heap.

public class Test {
    private static class HeapClass {
        public int y; // When an instance of HeapClass is allocated, this will be on the heap.
    }
    public static void main(String[] args) {
        int x=1; // This is on the stack.
    }
}

With regards to the update:

Objects do not have their own stack. In my example, int y would actually be part of each instance of HeapClass. Whenever an instance of HeapClass is allocated (e.g. new Test.HeapClass()), all member variables of HeapClass are added to the heap. Thus, since instances of HeapClass are being allocated on the heap, int y would be on the heap as part of an instance of HeapClass.

However, all primitive variables declared in the body of any method would be on the stack.

As you can see in the above example, int x is on the stack because it is declared in a method body--not as a member of a class.

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