Maybe I'm missing something but why does re-instantiating the array with zero elements not count as emptying it?

1. int [] foo = {1,2,3,4,5};
2. void setup() {
3.   println(foo.length);
4.   foo = new int[0];
5.   println(foo.length);
6. }

Alternatively you might consider using an ArrayList, which has a handy clear() method, instead of an array.

Finally it's not a good idea to make a repeated call to setup().  It does things internally and calling it again could potentially break things (or so I've been told).  Instead you're better off putting variable initialisations into a separate method (don't name this init() - you'll encounter a nasty name clash) and calling this from setup and wherever else it's required.  Then you can separate it from the peasycam initialisation ;)