code: private void trimToSize() {
  		if (wordsInUse != words.length) {
  			words = Arrays.copyOf(words, wordsInUse);
  			checkInvariants();
  		}
  	}
docs: Attempts to reduce internal storage used for the bits in this bit set.
  Calling this method may, but is not required to, affect the value
  returned by a subsequent call to the {@link #size()} method.