code: protected void swap(int i, int j) {
          byte[] ltemp = ranges[i];
          ranges[i] = ranges[j];
          ranges[j] = ltemp;
  
          String tempFilename = filenames[i];
          filenames[i] = filenames[j];
          filenames[j] = tempFilename;
      }
docs: Swaps the elements of the ith position with the elements of the jth position of all three arrays.