greenfoot error

some more information could be helpfull. If this error means that greenfoot doesn't start because of this invalid class you probably have to exchange it or reinstall greenfoot. But I'm not sure if this will help. Maybe someone of the greenfoot team can help you.

So Greenfoot will not start for you? It sounds like you might be using a really old version of Java? Or maybe your Greenfoot installation is corrupted. Anyway. For support on questions like this, please follow the instructions here .