public class MultiCrawlerThread implements Runnable {
    
    private final MultiCrawler multiCrawler;
    private final HtmlParser htmlParser = new HtmlParser();

    public MultiCrawlerThread(MultiCrawler multiCrawler) {
        super();
        this.multiCrawler = multiCrawler;
    }
    
    @Override
    public void run() {
        WebPage webPage;
        int getUnCrawlPageTimes = 0;
        while (true) {
            webPage = multiCrawler.getUnCrawlPage();
            if(webPage == null) {
                if(getUnCrawlPageTimes > 10) {
                    break;
                } else {
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    getUnCrawlPageTimes++;
                    continue;
                }
            }
            getUnCrawlPageTimes = 0;
            // your code here
        }
    }

}

public static final Integer MAX_THREADS = 20;
    
public void runThreads() throws InterruptedException {
    ExecutorService executorService = Executors.newFixedThreadPool(MAX_THREADS);
    for(int i = 0; i < MAX_THREADS; i++) {
        executorService.execute(new MultiCrawlerThread(this));
    }
    executorService.shutdown();
    executorService.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS);
}