code: private static void mergeInto(double[] first, double[] second) {
          for (int j = 0; j < first.length / 2; j++) {
              first[j] = Math.min(first[j], second[j]);
              first[j + first.length / 2] = Math.max(first[j + first.length / 2], second[j + first.length / 2]);
          }
      }
docs: Merges the second boundingbox into the first. Basically, this extends the first boundingbox to also
  encapsulate the second
  
  @param first  the first boundingbox
  @param second the second boundingbox