Just to augment the other answers from a different angle.
If you want to reuse hashcode(s) from 'above' and derive new ones using your class' immutatable state, then a call to super will work. While this may/may not cascade all the way up to Object (i.e. some ancestor may not call super), it will allow you to derive hashcodes by reuse.
@Override
public int hashCode() {
int ancestorHash = super.hashCode();
// now derive new hash from ancestorHash plus immutable instance vars (id fields)
}