code: private static boolean isUnM49AreaCode(String code) {
          if (code.length() != 3) {
              return false;
          }
  
          for (int i = 0; i < 3; ++i) {
              final char character = code.charAt(i);
              if (!(character >= '0' && character <= '9')) {
                  return false;
              }
          }
  
          return true;
      }
docs: A UN M.49 is a 3 digit numeric code.