right way to incorporate superclass into a Guava Objects.hashcode() implementation?

Question

Possibly a dumb question, but I don\'t want to screw this up. Let\'s say I have two Java classes, Class1 and Class2, where Class2 extends Class1

Answer 1

Effective Java does address this situation...by saying that you shouldn't do it. Item 8:

It turns out that this is a fundamental problem of equivalence relations in object-oriented languages. There is no way to extend an instantiable class and add a value component while preserving the equals contract, unless you are willing to forgo the benefits of object-oriented abstraction.

(Corollary: the same reasoning applies to hashCode().)