}

  private void drainQueue() throws Exception {
    for (HttpUrl url; (url = queue.take()) != null; ) {
      if (!fetchedUrls.add(url)) {
        continue;
      }

      Thread currentThread = Thread.currentThread();
      String originalName = currentThread.getName();
      currentThread.setName("Crawler " + url);
      try {
        fetch(url);
      } catch (IOException e) {

  }

  private void streamPrimesToSinkAsynchronously(final BufferedSink sink) {
    Thread thread = new Thread("writer") {
      @Override public void run() {
        try {
          sink.writeUtf8("Numbers\n");
          sink.writeUtf8("-------\n");
          for (int i = 2; i <= 997; i++) {
            System.out.println(i);
            Thread.sleep(10);
            sink.writeUtf8(String.format(" * %s = %s\n", i, factor(i)));
          }