code: public int[] next() {
  		if (!hasNext) return null;
  		int[] result = new int[r];
  		for (int i=0; i<r; i++) result[i] = index[i];
  		moveIndex();
  		return result;
  	}
docs: Get the next permutation.
  @return The next permutation, <code>null</code> if none exists.