线程池的正确调用

/**
 * @Description: 删除二维码图片
 * @author: huangbaiping
 * @date: 2017/12/13
 */
public class DelCodeJob {


private ScheduledExecutorService executor = Executors.newScheduledThreadPool(20);

private static DelCodeJob single = new DelCodeJob();

        // 单例
public static DelCodeJob getInstance() {
return single;
}

public void delCode(String imgUrl) {  
Runnable command = new Runnable() {
@Override
public void run() {
File f = new File(imgUrl);
f.delete();
}
};
executor.schedule(command, 3, TimeUnit.SECONDS);// 延迟三秒执行删除二维码图片
}

public static void main(String[] args) {
DelCodeJob.getInstance().delCode("");
}
}