code: @SuppressWarnings({ "unchecked" })
  	protected int compare(E k1, E k2) {
  		if (comparator == null) {
  			return ((Comparable) k1).compareTo(k2);
  		}
  		return comparator.compare(k1, k2);
  	}
docs: Compares two keys using the correct comparison method for this
  collection.