Here's the very first video. it's just me walking around:-
It's written in Java using the excellent JMonkeyEngine for the 3D. I did have a look at using LibGDX which is also very good. However, for the physics aspect at least, it was just a "leaky" wrapper for Bullet. Bullet is written in C, and so even in Java it seemed to be a case of remembering to dispose of objects and other things I'd hoped to never have to do again.