JAD is one of the best Java Decompiler today. This is one brilliant piece of software. Nevertheless, the last JDK supported by JAD 1.5.8 (Apr 14, 2001) is JDK 1.3.
DJ Java Decompiler, JadClipse, Cavaj and JarInspector are powered by Jad.
The last version of Decafe Pro has been released on 2002-01-03.
These viewers can not display Java 5 sources.
So, I use JD-GUI : logic, I'm the author :)