Is it possible to detect unused methods in a source tree using FindBugs? I see some posts on SO where users are claiming to do that, some others asking how to do this in FB
Well, since you want to go down this route despite warnings from the others who've responded :), you can copy and modify the UPM detector to do what you need.
Its really simple to write a detector for FindBugs (especially when you've got a great starting point). Read this to get you started