I installed JD-Eclipse from the update site but I can't get it to work in Eclipse Kepler. I've done this with previous versions of Eclipse with no problems.
The issue here is that when I go to Preferences > General > Editors > File associations, the default associated editor for the *.class files is "Class File Viewer (default) (locked by 'Java Class File' content type)". If I set the "Class File Editor" as default, the changes won't be saved.
How can I unlock the Class File Viewer?
As far as I know, try using admin privileges and open it in admin, if that doesn't work then do the usual uninstall and re-install or install Eclipse mars as it offers the best support currently for java program IMO