null parameter? Hot the hell is the class designed? These question I have often asked when I had was working with a library without sources. But now I have found a really nice Eclipse plugin http://java.decompiler.free.fr/jd-eclipse/. The update site is http://java.decompiler.free.fr/jd-eclipse/update.Now I may press F3 button and see the decompiled source immediately. I just miss a possibility to debug the code without source.
