code: public static HttpHubConnectionBuilder create(String url) {
          if (url == null || url.isEmpty()) {
              throw new IllegalArgumentException("A valid url is required.");
          }
          return new HttpHubConnectionBuilder(url);
      }
docs: Creates a new instance of {@link HttpHubConnectionBuilder}.
  
  @param url The URL of the SignalR hub to connect to.
  @return An instance of {@link HttpHubConnectionBuilder}.