I want to learn JOGL start with an existing engine, which one should I choose?

OpenGL Development JOGL Development
#1

I want to learn JOGL start with an existing engine, which one should I choose?
Is Xith3D suitable to start with?
Which one can be convered to JOGL easily?
Your suggestion is expected.
Thank you for giving me advices.

PS:Happy new year to everyone.

#2

I used the CVS to get the source of the Xith3D. It seems that the program have a few problems. Problems are reported with Eclipse.