Chunking a List into parts.

Needed to batch up the contents of a list into groups of 4 today. Spent a little more time than I would have liked on it, but I think it's a pretty neat bit of code now, and I actually got to use java.util.concurrent.CopyOnWriteArrayList for the first time.



The result of running this:

Top level list 1 contains:
1
2
3
4
Top level list 2 contains:
5
6
7
8
Top level list 3 contains:
9