To learn Java3D I'm creating a scriptable scene/level creator for Java game developers.
It's free and open source of course.https://sourceforge.net/projects/atomic3d/
Basic 3D scene creation and navigation. There's no reason you can't design a 2D tile-based level in it though.
Written in Java with Java3D
Scriptable scene control / object creation
Collada import and export (still very much under development, as no Java Collada library I've found works 100% so I have to learn Collada and write new filters)
Basic Obj Import
Export Java code directly (for e.g. Java3D demo)
Sunflow renderer integration
Networked "Collab" scene editing
MD5 formats, etc
It's starting to take shape, but probably not too useful yet with the possible exception of the Scripted Export.
But, if you have Eclipse and want to play with it to suggest features for your game levels feel free
There is a compiled Jar on the Sourceforge page