【并发编程】- 线程池使用remove删除未被执行的任务

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方法remove(Runnable)的使用

方法remove(Runnable)可以删除尚未被执行的Runnable任务。

运行类代码如下：

@Slf4j
public class RemoveRunnableRun {
    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                SimpleDateFormat simpleDateFormat = new SimpleDateFormat("HH:mm:ss");
                try {
                    System.out.println(Thread.currentThread().getName() + "  开始时间：" + simpleDateFormat.format(new Date()));
                    Thread.sleep(5000);
                    System.out.println(Thread.currentThread().getName() + "  结束时间：" + simpleDateFormat.format(new Date()));
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        };
        ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(1, 1, 5, TimeUnit.SECONDS, new LinkedBlockingQueue<>());
        threadPoolExecutor.submit(runnable);
        try {
            Thread.sleep(1000);
            threadPoolExecutor.remove(runnable);
            log.info("任务正在执行不能被删除！");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

运行结果如下：

pool-1-thread-1 开始时间：15:39:03 15:39:04.029 [main] INFO com.ozx.concurrentprogram.executor.controller.RemoveRunnableRun - 任务正在执行不能被删除！ pool-1-thread-1 结束时间：15:39:08

当多个任务添加到线程池中，remove操作会删除哪个任务

修改运行类代码如下：

@Slf4j
public class RemoveRunnableRun {
    private static SimpleDateFormat simpleDateFormat = new SimpleDateFormat("HH:mm:ss");
    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                try {
                    System.out.println(Thread.currentThread().getName() + "  开始时间：" + simpleDateFormat.format(new Date()));
                    Thread.sleep(5000);
                    System.out.println(Thread.currentThread().getName() + "  结束时间：" + simpleDateFormat.format(new Date()));
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        };

        Runnable secondRunnable = new Runnable() {
            @Override
            public void run() {
                try {
                    System.out.println(Thread.currentThread().getName() + "  开始时间：" + simpleDateFormat.format(new Date()));
                    Thread.sleep(5000);
                    System.out.println(Thread.currentThread().getName() + "  结束时间：" + simpleDateFormat.format(new Date()));
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        };
        ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(1, 1, 5, TimeUnit.SECONDS, new LinkedBlockingQueue<>());
        threadPoolExecutor.execute(runnable);
        threadPoolExecutor.execute(secondRunnable);
        try {
            Thread.sleep(1000);
            threadPoolExecutor.remove(secondRunnable);
            log.info("任务2未在运行能被删除！");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

运行结果如下：

pool-1-thread-1 开始时间：15:53:29 15:53:30.360 [main] INFO com.ozx.concurrentprogram.executor.controller.RemoveRunnableRun - 任务2未在运行能被删除！ pool-1-thread-1 结束时间：15:53:34

继续修改运行类代码如下：

@Slf4j
public class RemoveRunnableRun {
    private static SimpleDateFormat simpleDateFormat = new SimpleDateFormat("HH:mm:ss");
    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                try {
                    System.out.println(Thread.currentThread().getName() + "  开始时间：" + simpleDateFormat.format(new Date()));
                    Thread.sleep(5000);
                    System.out.println(Thread.currentThread().getName() + "  结束时间：" + simpleDateFormat.format(new Date()));
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        };

        Runnable secondRunnable = new Runnable() {
            @Override
            public void run() {
                try {
                    System.out.println(Thread.currentThread().getName() + "  开始时间：" + simpleDateFormat.format(new Date()));
                    Thread.sleep(5000);
                    System.out.println(Thread.currentThread().getName() + "  结束时间：" + simpleDateFormat.format(new Date()));
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        };
        ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(1, 1, 5, TimeUnit.SECONDS, new LinkedBlockingQueue<>());
        threadPoolExecutor.submit(runnable);
        threadPoolExecutor.submit(secondRunnable);
        try {
            Thread.sleep(1000);
            threadPoolExecutor.remove(secondRunnable);
            log.info("main线程 结束");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

运行结果如下：

pool-1-thread-1 开始时间：16:08:12

16:08:13.711 [main] INFO com.ozx.concurrentprogram.executor.controller.RemoveRunnableRun - main线程 结束

pool-1-thread-1 结束时间：16:08:17

pool-1-thread-1 开始时间：16:08:17

pool-1-thread-1 结束时间：16:08:22

从上述运行结果看出使用execute方法进行添加需要执行的任务，因为任务2并未运行，所以任务2被remove()方法成功删除，但使用submit()方法提交的任务未被执行时，使用remove()方法却不能删除此任务，所以任务2没有被删除。