Docco is a personal document retrieval tool based on Apache's Lucene indexing engine. It allows you to create an index for files on your file system which you can then search for keywords. It is not only a lot faster than searching by recursing through your file system every time, it also offers you extended query options like wildcards and fuzzy search as well as a visualization of result set intersections.
Most people tend to say: use Java or don't use Java. I think we should try to be more flexible in choosing our languages, currently I use a lot of Java because it seems practical but I definitely will try switch to something better designed for the next project (here are my 2c why Java is not well designed: http://www.peterbecker.de/texts/javacritique.html -- very early version, focus is on SW-Engineering/OO aspects).
The question is not if Linux needs Java or not, the question is neither if we should use Java or not, the question should be: is Java the appropriate tool for what you want to do. This is hard to figure out, but it is definitely worth some effort -- the programming language is one of the most important tools in your toolbox and you should choose your tools wisely (but without falling into analysis paralysis).
Trying to do everything with one language is like using a Leatherman to fix a car -- it will evolve into a huge and clumsy tool. And the usual argument that the costs of learning a new language are too high is short-sighted and usually ignores the fact that learning a language might give you some new insight -- esp. when it was hard to learn (assuming it is reasonable well designed).
And don't forget about tools like DBMS or Corba -- they allow you to use a number of different languages in one project. This has some drawbacks due to the overhead in build/deployment management and the fact that you need more skills in your team, but I think it is worth the effort and additionally ensures a clean design -- taking shortcuts across such boundaries is far harder than just declaring a private member public ;-)
Just some late thoughts,
PS: PhiRatE -- did you get to use all this languages on your job? When can I start? *g