code: public static IResolver defaultResolver() {
          return new IResolver() {
              @Override
              public Record[] resolve(Domain domain) throws IOException {
                  String[] addresses = defaultServer();
                  if (addresses == null) {
                      throw new IOException("no dns server");
                  }
                  IResolver resolver = new Resolver(InetAddress.getByName(addresses[0]));
                  return resolver.resolve(domain);
              }
          };
      }
docs: system ip would change