JAD/JadClipse is an invaluable tool for exploring Java APIs for which you do not have source codes. It should be a part of every Eclipse developer's installation. In this article, we'll see how we can set up this utility in Eclipse.
1. Download JAD decompiler from here http://hsapkota.com.au/downloads/jad158g.mac.intel.zip and unzip it somewhere in your system
2. Download JadClipse - the Eclipse plugin for JAD from here http://jadclipse.sourceforge.net/wiki/index.php/Main_Page#Download
3. Put JadClipse inside the plugins folder of your Eclipse installation
4. Set up preferences by giving path to the JAD decompiler to the plugin
5. Associate JadClipse to .CLASS files
Go to Preferences -> General -> Editors -> File Associations and associate .class and .class without source to Jadclipse File Viewer. Also make it default.
Double click a .CLASS file to see the decompiled data. The image below shows an example.