code: private <E> void listSwap(E[] list, int a, int b) {
  		final E tmp = list[a];
  		list[a] = list[b];
  		list[b] = tmp;
  	}
docs: Swaps two items in the given list.
  @param list list to swap the items in
  @param a index of the first item
  @param b index of the second item
  @param <E> list type