ScheduledExecutorService和ScheduledThreadPoolExecutor

定时任务的四种形式：

1.无返回值，入参Runnable

private static void testScheduledFutureRunnable() {
        ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(2);
        //Runnable
        ScheduledFuture<?> future1 = executor.schedule(() -> System.out.println("I will be invoked."), 2, TimeUnit.SECONDS);
        //如果被取消，Runnable里面的业务将不会被执行
        System.out.println(future1.cancel(true));
    }

2.有返回值，入参Callable

private static void testScheduledFutureCallable() throws InterruptedException, ExecutionException {
        ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(2);
        //Callable
        ScheduledFuture<Integer> future2 = executor.schedule(() -> 3, 2, TimeUnit.SECONDS);
        System.out.println(future2.get());
    }

3.以实际的任务执行时间为周期类似于Timer

private static void testScheduleAtFixedRate() {
        /**
         * period 2 seconds execute a task.
         * but the task spend 5 seconds actually
         * 
         * solution 1:(crontab/quartz/Control-M)
         * period first policy 周期优先策略
         * 
         * 这三种执行结果：
         * 0 : 5
         * 2 : 5
         * 4 : 5
         * 
         * solution 2 :(JDK Timer) 任务优先策略
         * 0 : 5
         * 5 : 5
         * 10: 5
         */
        ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(2);
        //任务优先--以实际的任务执行时间为周期
        final AtomicLong interval = new AtomicLong(0L);
        ScheduledFuture<?> future3 = executor.scheduleAtFixedRate(() ->
        {
            long currentTimeMillis = System.currentTimeMillis();
            if(interval.get() == 0) {
                System.out.printf("The first time trigger task at %d
", currentTimeMillis);
            } else {
                System.out.printf("The actually spend [%d]
", currentTimeMillis - interval.get());
            }
            
            interval.set(currentTimeMillis);
            System.out.println(Thread.currentThread().getName());
            
            try {
                TimeUnit.SECONDS.sleep(5);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, 1, 2, TimeUnit.SECONDS);
    }

4.以实际的任务执行时间+延长时间和为周期

private static void testScheduleWithFixedDelay() {
        ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(2);
        final AtomicLong interval = new AtomicLong(0L);
        //以实际的任务执行时间+延长时间和为周期
        ScheduledFuture<?> future4 = executor.scheduleWithFixedDelay(() -> {
            long currentTimeMillis = System.currentTimeMillis();
            if(interval.get() == 0) {
                System.out.printf("The first time trigger task at %d
", currentTimeMillis);
            } else {
                System.out.printf("The actually spend [%d]
", currentTimeMillis - interval.get());
            }
            
            interval.set(currentTimeMillis);
            System.out.println(Thread.currentThread().getName());
            
            try {
                TimeUnit.SECONDS.sleep(5);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, 1, 2, TimeUnit.SECONDS);
    }

两种方法：

1.scheduleAtFixedRate和getContinueExistingPeriodicTasksAfterShutdownPolicy配合使用

private static void test1() throws InterruptedException {
        ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(2);
        //打断之后允许周期性任务继续执行，默认false
        System.out.println(executor.getContinueExistingPeriodicTasksAfterShutdownPolicy());
        //true 允许周期性任务继续执行
        executor.setContinueExistingPeriodicTasksAfterShutdownPolicy(true);
        //任务优先--以实际的任务执行时间为周期
        final AtomicLong interval = new AtomicLong(0L);
        ScheduledFuture<?> future3 = executor.scheduleAtFixedRate(() ->
        {
            long currentTimeMillis = System.currentTimeMillis();
            if(interval.get() == 0) {
                System.out.printf("The first time trigger task at %d
", currentTimeMillis);
            } else {
                System.out.printf("The actually spend [%d]
", currentTimeMillis - interval.get());
            }
            
            interval.set(currentTimeMillis);
            System.out.println(Thread.currentThread().getName());
            
            try {
                TimeUnit.SECONDS.sleep(5);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, 1, 2, TimeUnit.SECONDS);
        
        TimeUnit.MILLISECONDS.sleep(1200);
        executor.shutdown();
    }

2.scheduleWithFixedDelay和getExecuteExistingDelayedTasksAfterShutdownPolicy配合使用

private static void test2() throws InterruptedException {
        ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(2);
        //被打断之后继续按照固定任务时间+延迟时间为周期执行，默认是true,被打断后继续执行当前任务
        System.out.println(executor.getExecuteExistingDelayedTasksAfterShutdownPolicy());
//        executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
        
        final AtomicLong interval = new AtomicLong(0L);
        //以实际的任务执行时间+指定周期时间和为周期
        ScheduledFuture<?> future4 = executor.scheduleWithFixedDelay(() -> {
            long currentTimeMillis = System.currentTimeMillis();
            if(interval.get() == 0) {
                System.out.printf("The first time trigger task at %d
", currentTimeMillis);
            } else {
                System.out.printf("The actually spend [%d]
", currentTimeMillis - interval.get());
            }
            
            interval.set(currentTimeMillis);
            System.out.println(Thread.currentThread().getName());
            
            try {
                TimeUnit.SECONDS.sleep(5);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, 1, 2, TimeUnit.SECONDS);
        
        TimeUnit.MILLISECONDS.sleep(1200);
        executor.shutdown();
    }