code: public static boolean hasLiteralIPAddress(URI resource) {
          String host = resource.getHost();
          if ( host == null || host.isEmpty() ) {
              return false;
          }
          // basic check for a '.'-separated numeric string for now
          return host.matches("([0-9A-Fa-f]|\\.){4,16}");
      }
docs: We can make this tighter but IPAddressUtil is in a sun package sadly