Learn how to use the standard Java APIs before jumping into third party libraries.
I sort of disagree there.
If you start out with a clear goal, using a dedicated gaming library can help keeping things fun (provided that library has some good tutorials).
Of course you can start out with pure java, but getting anything remotely playable out of it is probably more difficult than just using some easy to use game library.
IMHO the most motivating way to learn something is by having FUN doing it."Wow, see that cube spin in 3D! Let's see how I can make it move!"
, that sort of thing.
Learning the intricacies behind it *will* come, just as long as you can keep yourself motivated by having fun learning.
When I learned java, my first project was an emulator of the Pacman arcade (which then later grew to become something of scale I could never have imagined when I started).
Not because it made sense to start with something like that as a java newbie, but because I was really interested in emulators and I already knew about Z80 assembly (but jack shit about java).
To *me* it made sense and it while I was punching above my weight at the time I started out, pure motivation kept me going and eventually helped me learning java.