code: private static void compressLongestRunOfZeroes(int[] hextets) {
      int bestRunStart = -1;
      int bestRunLength = -1;
      int runStart = -1;
      for (int i = 0; i < hextets.length + 1; i++) {
        if (i < hextets.length && hextets[i] == 0) {
          if (runStart < 0) {
            runStart = i;
          }
        } else if (runStart >= 0) {
          int runLength = i - runStart;
          if (runLength > bestRunLength) {
            bestRunStart = runStart;
            bestRunLength = runLength;
          }
          runStart = -1;
        }
      }
      if (bestRunLength >= 2) {
        Arrays.fill(hextets, bestRunStart, bestRunStart + bestRunLength, -1);
      }
    }
docs: Identify and mark the longest run of zeroes in an IPv6 address.
  
  <p>Only runs of two or more hextets are considered. In case of a tie, the leftmost run wins. If
  a qualifying run is found, its hextets are replaced by the sentinel value -1.
  
  @param hextets {@code int[]} mutable array of eight 16-bit hextets