JD-GUI is a standalone graphical utility that displays Java source codes of “.class” files. You can browse the reconstructed source code with the JD-GUI for instant access to methods and fields. JD-GUI is free for non-commercial use. This means that JD-GUI shall not be included or embedded into commercial software products. Nevertheless, this project may be freely used for personal needs in a commercial or non-commercial environments.

Download
http://java.decompiler.free.fr/jd-gui/downloads/jd-gui-0.3.3.windows.zip
http://java.decompiler.free.fr/jd-gui/downloads/jd-gui-0.3.3.linux.i686.tar.gz