}
        };
        CrawlingParameterUtil.setUrlQueueService(service);
        assertNotNull(CrawlingParameterUtil.getUrlQueueService());

        // Set to null
        CrawlingParameterUtil.setUrlQueueService(null);

        // Should be null now
        assertNull(CrawlingParameterUtil.getUrlQueueService());
    }

 * CrawlingParameterUtil.setCrawlerContext(newContext);
 *
 * UrlQueueService<UrlQueue<?>> urlQueueService = CrawlingParameterUtil.getUrlQueueService();
 * CrawlingParameterUtil.setUrlQueueService(newUrlQueueService);
 *
 * DataService<AccessResult<?>> dataService = CrawlingParameterUtil.getDataService();
 * CrawlingParameterUtil.setDataService(newDataService);
 * }
 * </pre>
 *

        int threadCheckCount = 0;
        // set urlQueue to thread
        CrawlingParameterUtil.setCrawlerContext(crawlerContext);
        CrawlingParameterUtil.setUrlQueueService(urlQueueService);
        CrawlingParameterUtil.setDataService(dataService);
        try {
            while (crawlerContext.getStatus() != CrawlerStatus.DONE && isContinue(threadCheckCount)) {