I think you should probably decide if you want to make a 2D or 3D game before you look for a good graphics engine as there are a lot of graphic engines that are good at 2D or 3D, but not the other (at least for other languages; I'm not sure about Java)
If you're just starting out, I would highly recommend sticking to 2D until you have some experience
As far as I know, Java isn't exactly the most beloved programming language for doing games, but some googling reveals that there is LibGDB
for doing 2D games in Java, so you could give those a try
I can't recall of hearing of either before, though, so I don't know if they'll work well. Personally, if you're just starting out with programming, I'd recommend something like GameMaker, but you probably already know that from your other thread
Still, please don't be put off by my somewhat salty view of Java game development, and feel free to post any questions that you have
Even if we don't know the engine that you're using, we still may be able to help.