What kind of memory will allocate in Java?

Question

Someone kindly clear my doubt on memory management in Java with the below-mentioned scenario.

When we assign value for the primitive data type variable the value will be stored in stack memory. Please do correct me if I understood the concept wrong.

As same like how the memory will allocate when do assign a value of a non-primitive data type as mentioned below.

Integer a = 3;

Will create a memory in stack or heap?

Either. It depends whether it is method-local or a class member. — user207421, Aug 02 '19 at 06:11
Possible duplicate of https://stackoverflow.com/questions/8419860/integer-vs-int-with-regard-to-memory — Ashwani, Aug 02 '19 at 06:13
What happens when we declare the variable as method-local and class member? Please do clear my doubt on this. @user207421 — Bhuvanesh Waran, Aug 02 '19 at 06:16
You *can't* declare it as both method-local *and* a class member. One or the other. Make up your mind. But I now see you wrote `Integer` instead of `int`, which means the object is on the heap. I was referring to where the *variable* `a` is located. — user207421, Aug 02 '19 at 06:18
Am not saying that I will declare the same variable as class member and method local. Am just asking how memory will allocate when we declare as class member and when we declare as method-local — Bhuvanesh Waran, Aug 02 '19 at 06:23
If the variable `a` is method-local, it is on the stack. If it is a class member: on the heap. The `Integer` object it refers to is always on the heap. — user207421, Aug 02 '19 at 06:29

Stephen C · Accepted Answer · 2019-08-02T07:38:16.410

The variable a will be either in heap or stack memory depending on what kind of variable it is:

method or constructor local variables (including parameters) - on the stack
instance variables (aka attributes or fields) - on the heap
class variables - on the heap.

^{(For the sake of completeness, there are couple of obscure cases where a lambda or inner class refers to an effectively final local variable in an enclosing scope. In those cases, a copy of the original variable's contents will be stored on the heap.)}

The Integer object that represents the boxed value of 3 will be on the heap.

A copy of the reference to that object is stored in the variable a wherever that happens to be. There may be other copies of that reference elsewhere in the JVM.

What kind of memory will allocate in Java?

1 Answers1