the problem runs deeper. When version 2 of the ThirdParty class ships, suddenly your class doesn't work. If another team has subclassed your class and overridden your printResult routine, you are effectively stuck. You can't take in bug fixes that exists in version 2 and the other team effectively couldn't move forward either. Remember, this is best practice OO, and there really hasn't been any changes to the interface. So effectively this is like version 1.01.

It is namespace pollution of a very subtle and devious kind.