code: public <T extends WebCrawler> void startNonBlocking(Class<T> clazz, int numberOfCrawlers) {
          start(new DefaultWebCrawlerFactory<>(clazz), numberOfCrawlers, false);
      }
docs: Start the crawling session and return immediately.
  This method utilizes default crawler factory that creates new crawler using Java reflection
  
  @param clazz
  the class that implements the logic for crawler threads
  @param numberOfCrawlers
  the number of concurrent threads that will be contributing in
  this crawling session.
  @param <T> Your class extending WebCrawler