question: protected Key ( int privatekey ) { this . privatekey = privatekey ; recordIdentity ( this ) ; }
target:  Construct a key using the indicated private key.  Each subclass of Key maintains its own unique domain of integer keys.  No two objects with the same integer key and of the same specific subclass can be constructed.  An exception will be thrown if an attempt is made to construct another object of a given class with the same integer key as a pre-existing instance of that subclass of Key.