How does the JVM ensure that System.identityHashCode() will never change?

Question

Typically the default implementation of Object.hashCode() is some function of the allocated address of the object in memory (though this is not

Answer 1

The general guideline for implementing a hashing function is :

• the same object should return a consistent hashCode, it should not change with time or depend on any variable information (e.g. an algorithm seeded by a random number or values of mutable member fields
• the hash function should have a good random distribution, and by that I mean if you consider the hashcode as buckets, 2 objects should map to different buckets (hashcodes) as far as possible. The possibility that 2 objects would have the same hashcode should be rare - although it can happen.