Object.hashcode VS System.identityHashCode

basically System.identityHashCode (Object) always returns different values for different objects
Its declared as public static int identityHashCode(Object x)

The hash code for the null reference is zero.

// FileName Test.java
class HashCodeTest
{
    int number;
    public HashCodeTest(int i)
    { this.number=i;}

    public int hashCode() { return this.number; }
}

public class Test
{
    public static void main(String[] args)
    {
        String s1="Namaste"; String s2 = s1;
        System.out.println("s1 "+ s1 + " s2 "+ s2);
        System.out.println("System.identityHashCode(s1)"  + System.identityHashCode(s1));
        System.out.println("System.identityHashCode(s2) "+ System.identityHashCode(s2));
        s1=s1 + " World";
        System.out.println(" s1 "+ s1 + " s2 " + s2);
        System.out.println("System.identityHashCode(s1) " + System.identityHashCode(s1));
        System.out.println("System.identityHashCode(s2) "+ System.identityHashCode(s2));

        HashCodeTest o1 = new HashCodeTest(5);
        HashCodeTest o2 = new HashCodeTest(5);

        System.out.println("");
        System.out.println("First Object : " + o1);
        System.out.println("Second Object : " + o2);
        System.out.println("System.identityHashCode(First_Object) : " + System.identityHashCode(o1));
        System.out.println("System.identityHashCode(Second_Object) : " + System.identityHashCode(o2));
    }
}

the output was something like


s1 Namaste s2 Namaste
System.identityHashCode(s1)1671711
System.identityHashCode(s2) 1671711
s1 Namaste World s2 Namaste
System.identityHashCode(s1) 11394033
System.identityHashCode(s2) 1671711

First Object : HashCodeTest@5
Second Object : HashCodeTest@5
System.identityHashCode(First_Object) : 4384790
System.identityHashCode(Second_Object) : 9634993