How to Access Variable's Memory Address In Java? [duplicate]

Question

I wrote this code and want to see memory location of 2 objects that i create from one class and make instance of one specific variable.

public class StaticFields { int a = 12; int b = 235; public static void main(String[] args) { StaticFields obj = new StaticFields(); int a = obj.a; StaticFields obj2 = new StaticFields(); int c = obj2.a; System.out.println(System.identityHashCode(a)); System.out.println(System.identityHashCode(c)); } }

why the "identityHashCode" of "a" and "c" is the same ?

Thanks.

FYI: The value returned by identityHashCode() has nothing to do with memory address. In general, you cannot get the memory address of an object in Java. — Andreas
– Andreas, Commented Oct 9, 2019 at 11:36
a and c are both primitive int values, so when you call identityHashCode() which expects an Object, the compiler will autobox the values to Integer objects, and values in range -128 to 127 are cached for performance, so you get the same Integer object every time you call the method with value 12. — Andreas
– Andreas, Commented Oct 9, 2019 at 11:39
here is another SO-thread on that matter. Including a "workaround" on how to extrapolate the heap-address from an object (the one you see when you use the toString() method of a class that does not override it) — GameDroids
– GameDroids, Commented Oct 9, 2019 at 11:45
@Andreas thank you for the clarification, I removed my comment. — GameDroids
– GameDroids, Commented Oct 9, 2019 at 11:48

TheSemicolon · Accepted Answer · 2019-10-09 11:53:04Z

-2

Both the integers carry the same value, 12.

Since Integers are cached (for values up to 127 from -128), the hash code value of both objects returned are same.

This is not true for b since its value is greater than 127.

edited Oct 9, 2019 at 11:53

answered Oct 9, 2019 at 11:38

TheSemicolon

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4 Comments

Andreas Over a year ago

The value of an int has nothing to do with identityHashCode() of an Object (parameter type of the method).

Seelenvirtuose Over a year ago

Try it with obj.b and obj2.b. They have also "the same value", but ...

TheSemicolon Over a year ago

@Seelenvirtuose - hashcode value of obj.b and obj2.b is not same.

Aryan Gates Over a year ago

Thanks for answers . now , my problem is int c and int a has the same memory location ? i mean are they point to one location of memory ? or they have different objects in memory cause they are from separate instance ?

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