How do JVMs implement IdentityHashMap?

Question

Specifically when they're used with a moving garbage collectors. The current memory location of the object can't be used because it can change at the next collection, so what is used as the objects hash?

Answer 1

Hope this question helps: How does the JVM ensure that System.identityHashCode() will never change?

Also http://xiao-feng.blogspot.com/2007/04/object-hashcode-implementation.html