code: @Override
  	public boolean retainAll(IntSet c) {
  		if (c == null || c.isEmpty())
  			return false;
  		IntIterator itr = iterator();
  		boolean res = false;
  		while (itr.hasNext()) {
  			int e = itr.next();
  			if (!c.contains(e)) {
  				res = true;
  				itr.remove();
  			}
  		}
  		return res;
  	}
docs: {@inheritDoc}