runStart = -1;
      }
    }
    if (bestRunLength >= 2) {
      Arrays.fill(hextets, bestRunStart, bestRunStart + bestRunLength, -1);
    }
  }

  /**
   * Convert a list of hextets into a human-readable IPv6 address.
   *
   * <p>In order for "::" compression to work, the input should contain negative sentinel values in
   * place of the elided zeroes.
   *