Java is used more in open source (Score 1)

I'd say learn java if you're a linux freak. If you check out freshmeat.net, you'll see that java is used in 4000 projects while c# is used in 300. So if you want to get on board with an open source project, java is the way to go. Also, since there's a vm for java on linux, it'll make your homework easier to do (if you only use linux boxes).