Why hashCode() returns the same value for a object in all consecutive executions?

Question

I am trying some code around object equality in java. As I have read somewhere

hashCode() is a number which is generated by applying the hash function. Hash Function can be different for each object but can also be same. At the object level, it returns the memory address of the object.

Now, I have sample program, which I run 10 times, consecutively. Every time i run the program I get the same value as hash code.

If hashCode() function returns the memory location for the object, how come the java(JVM) store the object at same memory address in the consecutive runs?

Can you please give me some insight and your view over this issue?

The Program I am running to test this behavior is below :

public class EqualityIndex {

    private int index;

    public EqualityIndex(int initialIndex) {
       this.index = initialIndex;
    }

    public static void main(String[] args) {
        EqualityIndex ei = new EqualityIndex(2);
        System.out.println(ei.hashCode());
    }

}

Every time I run this program the hash code value returned is 4072869.

Answer 1

how come the java(JVM) store the object at same memory address in the consecutive runs?

Why wouldn't it? Non-kernel programs never work with absolute memory addresses, they use virtual memory where each process gets its own address space. So it's no surprise at all that a deterministic program would place stuff at the same location in each run.

Answer 2

Well, the objects may very well end up in the same location in the virtual memory. Nothing contradictory with that. Bottom line is that you shouldn't care anyway. If the hashCode is implemented to return something related to the internal storage address (there is no guarantee at all!) there is nothing useful you could do with that information anyway.