What you're looking for is a free Java Integrated Development Environment (IDE). Netbeans (http://www.netbeans.org) meets your requirement (free as in beer and free like "mozilla" source code...)
Some reviewers think netbeans 4.1 is pretty good:
http://javaboutique.internet.com/reviews/netbeans41/
(newer netbeans are getting faster, newer releases of eclipse seem to be getting slower.)
Look out for netbeans 5.0!
http://www.netbeans.org/community/releases/50/index.html