Fact: a large application developed and maintained by several people, we ended up having a lot of dead code ...
A first solution is to use the clean up of Eclipse, one arrives to remove some attributes not used ... but it does not go much further.
The idea would be much more radical: a tool to pass on all the code.
Fortunately (again), Eclipse is saving our lives 
- Let's start by downloading Eclipse Core Tools: http://www.eclipse.org/eclipse/platform-core/updates/
- Select Project / package / class on which to pass the tool
- Via the shortcut menu, click Find Unreferenced Members. The search result is displayed in the Search View
- Get the ax ...
By cons, beware: it is possible that some classes appear to be unused when they are called by an extension point!
