ScheduledThreadPoolExecutor取消任务时并删除_scheduledthreadpool 删除任务

ScheduledThreadPoolExecutor取消任务时并删除

 public static void main(String[] args) throws InterruptedException {
        ScheduledThreadPoolExecutor executor = (ScheduledThreadPoolExecutor) Executors.newScheduledThreadPool(2);
        //如果为true,则 任务取消的时候 会从队列中把这个任务删除，默认是false
        //在默认的情况下，如果直接取消，并不会删除队列中的任务，反而会造成内在泄露
        executor.setRemoveOnCancelPolicy(true);
        ScheduledFuture<?> task = executor.scheduleAtFixedRate(() -> {
            System.out.println(Thread.currentThread().getName() + " running...");
        }, 0, 500, TimeUnit.MILLISECONDS);
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    try {
                        TimeUnit.SECONDS.sleep(1);
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                    int size = executor.getQueue().size();
                    System.out.println(Thread.currentThread().getName() + " queue size:" + size);
                }
            }
        }, "monitor-thread").start();
        TimeUnit.SECONDS.sleep(4);
        task.cancel(true);
        System.out.println(Thread.currentThread().getName() + " cancel the task..");


    }

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结果

pool-1-thread-1 running...
pool-1-thread-1 running...
monitor-thread queue size:1
pool-1-thread-1 running...
pool-1-thread-1 running...
monitor-thread queue size:1
pool-1-thread-1 running...
pool-1-thread-1 running...
monitor-thread queue size:1
pool-1-thread-1 running...
pool-1-thread-1 running...
main cancel the task..
monitor-thread queue size:0
monitor-thread queue size:0
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