Open source, pure Java physics / dynamics library [closed]

Answer 1

I have used JBullet and JBox2D. They both are good libraries. JBox2D is more actively being changed, but JBullet has slightly larger base.

Just for fun, I was trying to simulate an old physics problem recently, for which I posted the results here.

Answer 2

I would also use JBullet, though its been a couple of years since I last worked with it.