private void doWork() {
		System.out.println("DeleteWorker start to work!");
		long start = System.currentTimeMillis();
		for (String file : files) {
			FileReaderUtils.del(file);
		}
		long end = System.currentTimeMillis();
		long period = end - start;
		System.out.println("Deleting files cost time in millis : " + period);
		if (period < 2000) {
			try {
				Thread.sleep(2000);
				System.out.println("Sleeping 2 seconds");
			} catch (InterruptedException ie) {
				ie.printStackTrace();
			}
		}
		try {
			VideoDao.instance().writeToIniFile();
		} catch (IOException e1) {
			e1.printStackTrace();
		}
		System.out.println("Sleep 2 seconds");
		this.downLatch.countDown();
		System.out.println("DeleteWorker task finished!");
	}