code: public static int cardinality(SkippableIterator i) {
  		int card = 0;
  		while (i.hasValue()) {
  			card += Integer.bitCount(i.getCurrentWord());
  			i.advance();
  		}
  		return card;
  	}
docs: Cardinality.
  
  @param i
  the i
  @return the int