scheduleExecutor终止指定任务的方式

使用ScheduledExecutorService.schedule提交任务到执行器定时执行后，我们想在某一特定条件下终止执行器中的某个任务。本文列举2种实现方法。

import java.util.concurrent.*;

/**
 * @author bigbird
 * @Description: ${描述}
 */
public class Test {

    public static void main(String[] args) throws Exception {
        ConcurrentHashMap<String, ScheduledFuture> taskMap = new ConcurrentHashMap<>(4);

        ScheduledExecutorService scheduleExecutor = new ScheduledThreadPoolExecutor(3);
        ScheduledFuture scheduledFutureI = scheduleExecutor.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                System.out.println("--------------------------------");
                for (int i = 0; i < 10; i++) {
                    System.out.println(Thread.currentThread().getName() + ",i=" + i);
                }
            }
        }, 1, 2, TimeUnit.SECONDS);
        taskMap.put("scheduledFutureI", scheduledFutureI);

        ScheduledFuture scheduledFutureJ = scheduleExecutor.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                System.out.println("--------------------------------");
                for (int j = 0; j < 10; j++) {
                    if (j == 3) {
                        //方式1：通过在任务内部抛出异常的方式终止任务
                        System.out.println("scheduledFuture2终止...");
                        throw new RuntimeException();
                    }
                    System.out.println(Thread.currentThread().getName() + ",j=" + j);
                }
            }
        }, 1, 2, TimeUnit.SECONDS);
        taskMap.put("scheduledFutureJ", scheduledFutureJ);

        ScheduledFuture scheduledFutureK = scheduleExecutor.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                System.out.println("--------------------------------");
                for (int k = 0; k < 10; k++) {
                    if (k == 6) {
                        //方式2：通过cancel方式终止任务
                        System.out.println("scheduledFuture3终止...");
                        taskMap.get("scheduledFuture3").cancel(true);
                    }

                    System.out.println(Thread.currentThread().getName() + ",k=" + k);
                }
            }
        }, 1, 1, TimeUnit.SECONDS);
        taskMap.put("scheduledFutureK", scheduledFutureK);

        Thread.sleep(10000);
        //如果注释下面一行,scheduleExecutor不被shutdown,则scheduledFutureI将一直被执行
        scheduleExecutor.shutdown();
        System.out.println("主线程终止 " + Thread.currentThread().getName() + ",调度器关闭");

        //运行该程序,可以发现scheduledFutureJ和scheduledFutureK分别在特定条件下使用了不同的方式终止执行,scheduledFutureI一直正常运行,直到scheduleExecutor被shutdown
    }
}

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