final CmdLineParser parser = new CmdLineParser(options);
        try {
            parser.parseArgument(args);
        } catch (final CmdLineException e) {
            System.err.println(e.getMessage());
            System.err.println("java " + Crawler.class.getCanonicalName() + " [options...] arguments...");
            parser.printUsage(System.err);
            return;
        }

      if (responseCode != 200 || contentType == null) {
        return;
      }

      MediaType mediaType = MediaType.parse(contentType);
      if (mediaType == null || !mediaType.subtype().equalsIgnoreCase("html")) {
        return;
      }

      Document document = Jsoup.parse(response.body().string(), url.toString());
      for (Element element : document.select("a[href]")) {
        String href = element.attr("href");