I’ve never heard of Processing before, so I wouldn’t know how to compare Java to it (I’m no expert either 
). I’ve checked it out, and the kind of stuff one can do with it is really cool.
Regarding Javascript, If you’re into learning it to do the same type of work that can be done with Processing, check out geldoot on codepen. He has some amazing code there. One can learn a lot just by studying it.