Inspecting .class files

Sometimes, it's hard to tell exactly what version of a class has made it onto a server. Maybe you've overridden a method in code, but your implementation never seems to be called. It could be that the actual class on the server is an old, cached version without your change.

http://www.ej-technologies.com/products/jclasslib/overview.html

jClassLib is a handy little util for opening up compiled .class files and seeing what's in them: fields, methods, the lot.