java hashCode() function on reference variable and objects

Question

For example, if I create an A type object,

A a = new A();

then a is a reference on the Stack that points to a A type object on the heap. My question is, if I call a.hashCode(), which one's hash code will be returned, the hashcode of the reference or the hashcode of the object? if it is the hashcode of the object, how can i get the hashcode of the reference? Could anyone kindly give me some tips plz?

Answer 1

hashCode() is just a non-static method, just like any other non-static method. It's either defined by A, or by a base class of A (Object, in the worst case). All that happens is that method gets called on the instance in question.

how can i get the hashcode of the reference?

You can't, because that doesn't make sense.

Answer 2

You can get the hash code of the reference by calling:

System.identityHashCode(a);

This is what data structures such as java.util.IdentityHashMap are based on.