System.out.println("Usage: Crawler <cache dir> <root>");
      return;
    }

    int threadCount = 20;
    long cacheByteCount = 1024L * 1024L * 100L;

    Cache cache = new Cache(new File(args[0]), cacheByteCount);
    OkHttpClient client = new OkHttpClient.Builder()
        .cache(cache)
        .build();

    Crawler crawler = new Crawler(client);
    crawler.queue.add(HttpUrl.get(args[1]));

            if (logger.isDebugEnabled()) {
                logger.debug("Crawler is stopped.", e);
            } else if (logger.isInfoEnabled()) {
                logger.info("Crawler is stopped.");
            }
            exitCode = Constants.EXIT_FAIL;
        } catch (final Throwable t) {
            logger.error("Crawler does not work correctly.", t);
            exitCode = Constants.EXIT_FAIL;
        } finally {