}
      return array;
    }

    /** Number of bits */
    long bitSize() {
      return (long) data.length() * Long.SIZE;
    }

    /**
     * Number of set bits (1s).
     *
     * <p>Note that because of concurrent set calls and uses of atomics, this bitCount is a (very)
     * close *estimate* of the actual number of bits set. It's not possible to do better than an

   *
   * <p>In order for "::" compression to work, the input should contain negative sentinel values in
   * place of the elided zeroes.
   *
   * @param hextets {@code int[]} array of eight 16-bit hextets, or -1s
   */
  private static String hextetsToIPv6String(int[] hextets) {
    // While scanning the array, handle these state transitions:
    //   start->num => "num"     start->gap => "::"