code: @Override
    public void complement()
    {
      if (isEmpty()) {
        return;
      }
      if (size > 0) {
        size = last() - size + 1;
      }
      int lastWordMask = ALL_ONES_WORD >>> Integer.numberOfLeadingZeros(words[firstEmptyWord - 1]);
      final int[] localWords = words;       // faster
      for (int i = 0; i < firstEmptyWord - 1; i++) {
        localWords[i] ^= ALL_ONES_WORD;
      }
      localWords[firstEmptyWord - 1] ^= lastWordMask;
      fixFirstEmptyWord();
    }
docs: {@inheritDoc}