Steps to add the Java Decompiler in Eclipse :

http://jd.benow.ca/

Release

• jd-eclipse-site-1.0.0-RC2.zip
  Size : 579 KB

Source code

•  
  github.com/java-decompiler/jd-eclipse
   

Installation

1. Download and unzip the JD-Eclipse Update Site,
2. Launch Eclipse,
3. Click on "Help > Install New Software...",
4. Click on button "Add..." to add an new repository,
5. Enter "JD-Eclipse Update Site" and select the local site directory,
6. Check "Java Decompiler Eclipse Plug-in",
7. Next, next, next... and restart Eclipse.

To Add the Class patterns follow the following steps.

To Make it work in Eclipse Poton- 

I had to do some additional steps.

Eclipse -> Windows -> Preferences ->General -> Editors -> File Association

1. Select "*.class" and mark "Class File Editor" as default
2. Select "*.class without source" -> Add -> "Class File Editor" -> Make it as default
3. Add "*.jar" in FileTypes and -->Add -> "Class File Editor" -> Make it as default
4. Add "*.war" in FileTypes and -->Add -> "Class File Editor" -> Make it as default
5. Restart eclipse