docs: public static boolean isDotQuadIP ( String hostname ) {
          if ( Character.isDigit(hostname.charAt(0)) ) {
              int i, len, dots;
              char[] data;
  
              i = dots = 0; /* quick IP address validation */
              len = hostname.length();
              data = hostname.toCharArray();
              while ( i < len && Character.isDigit(data[ i++ ]) ) {
                  if ( i == len && dots == 3 ) {
                      // probably an IP address
                      return true;
                  }
                  if ( i < len && data[ i ] == '.' ) {
                      dots++;
                      i++;
                  }
              }
          }
  
          return false;
      }