i spend about one hour to find this nasty error. i was checking some methods of the class Collections, but using sort() with my own object i always got a ClassCastExeception and i couldn't find out why: my object Car was properly implementing the comparable interface. but then i saw a strange looking import statement in my code and it dawns on me: my current example used the class Car that i had implemented in a previous example with Arrays stored in an other package, that has no comparable interface implemented. shame on me :o. can you report about similar (silly) situations as a java programmer?