I recently carried out a trawl of the internet to find all the open-source Java Voxel Engines I could. My intention is to use one of them as a foundation to write my own voxel-based game (which is still a long way off). I didn't spend too long on each one; I simply checked that they worked and that they included all relevant code. Here are my results which others may find useful.
Firstly, the best ones I found. (As an aside, one of my general requirement is that an open-source project should work, once all dependencies have been resolved, and these should be resolvable easily. What's the point of releasing source code that doesn't work?) These all worked:-
* https://github.com/MovingBlocks/Terasology - You could say this was the best of the lot. It worked first time and looks amazing. The only drawback is its complexity; there's loads of code and loads of dependencies and libraries.
* https://github.com/mk12/mycraft - This is a great simple engine. It's only about 8 classes big but provides a nice simple voxel engine in Java.
* http://borderterrierart.weebly.com/programming.html (BlockWorld) - This one seemed to fit my requirements best. It's got lots of features including .obj model loading, and worked first time. The only drawback is that the source is a bit messy (formatting, unused vars etc..)
* https://github.com/Zaneris/Tranquil - This worked well, and since it uses LibGDX could work on mobile devices as well as PCs.
* https://github.com/aaasen/voxel-party - This worked, although it didn't have any textures.
* https://github.com/matortheeternal/JVoxelEngine - This uses raycasting. Seemed very slow and simple, and although it worked, it was very bare-bones.
I couldn't get these to work:-
* https://github.com/SpoutDev/Spout - Seems very worthy, but I couldn't get it to work as the Maven build fails.
* https://github.com/afaulconbridge/ArdorCraft - Couldn't get this to work due to missing source.
The following use JMonkeyEngine which I haven't tried:-
And I also found these two projects which are not voxels, but rather "traditional" 3D but still worked very well:-
That's pretty much all I could find. I hope you find it useful. I'd be interested to know if anyone has found any more, and which one's they found the best?