code: public void ensureCapacity(int requiredBits)
      {
          int requiredWords = wordIndex(requiredBits - 1) + 1;
          if (words.length < requiredWords)
          {
              long[] newWords = new long[requiredWords];
              System.arraycopy(words, 0, newWords, 0, words.length);
              words = newWords;
          }
      }
docs: Ensures that the BitSet can hold enough bits.
  @param requiredBits the required number of bits.