code: private String format(int[] octets) {
          StringBuilder str = new StringBuilder();
          for (int i =0; i < octets.length; ++i){
              str.append(octets[i]);
              if (i != octets.length - 1) {
                  str.append(".");
              }
          }
          return str.toString();
      }
docs: /*
  Convert a 4-element array into dotted decimal format