code: private void ensureCapacity(int wordsRequired)
    {
      if (words.length >= wordsRequired) {
        return;
      }
      int newLength = Math.max(words.length << 1, wordsRequired);
      words = Arrays.copyOf(words, newLength);
    }
docs: Ensures that the {@link FastSet} can hold enough words.
  
  @param wordsRequired the minimum acceptable number of words.