取消正在执行的线程

Posted 2022-09-03 zhangjin1120

Future调用cancel(true)后，仍然在执行？

开一个线程，执行一个任务：计算1000000033是不是质数，2秒后取消这个任务。
真的是：不试不知道，一试吓一跳！！！

public class FutureTest 

    public static void main(String[] args)
        ExecutorService threadPool = Executors.newSingleThreadExecutor();
        Future<Boolean> future = threadPool.submit(new Callable<Boolean>() 
            @Override
            public Boolean call()throws Exception 
                // i < num 让任务有足够的运行时间
                long num = 1000000033L;
                for (long i = 2; i < num; i++) 

                    if (num % i == 0) 
                        return false;
                     else if (i % 100000000 == 0) 
                        System.out.print("i=" + i + "  ");
                        if (i % 600000000 == 0) 
                            System.out.println("\\n");
                        
                    
                
                return true;
            
        );
        threadPool.shutdown(); // 发送关闭线程池的指令
        cancelTask(future, 2000); //2秒后取消任务

        try 
            boolean is = future.get();
            System.out.println("--------------------------------------------is:" + is + "-----------------------");
         catch (CancellationException ex) 
            System.err.println("\\n\\n\\n任务被取消\\n\\n\\n");
         catch (InterruptedException ex) 
            System.err.println("当前线程被中断");
         catch (ExecutionException ex) 
            System.err.println("任务执行出错");
        


    


    private static void cancelTask(Future<?> future, int delay) 
        new Thread(new Runnable() 
            @Override
            public void run() 
                try 
                    Thread.sleep(delay);
                    future.cancel(true); // 取消与 future 关联的正在运行的任务
                 catch (InterruptedException ex) 
                    ex.printStackTrace(System.err);
                
            
        ).start();
    

完整的取消方法

在for循环里面添加判断：

                    if (Thread.currentThread().isInterrupted())  // 任务被取消
                        System.out.println("PrimerTask.call： 你取消我干啥？");
                        return false;
                    

完整方法如下：

public class FutureTest 

    public static void main(String[] args)
        ExecutorService threadPool = Executors.newSingleThreadExecutor();
        Future<Boolean> future = threadPool.submit(new Callable<Boolean>() 
            @Override
            public Boolean call()throws Exception 
                // i < num 让任务有足够的运行时间
                long num = 1000000033L;
                for (long i = 2; i < num; i++) 
                    if (Thread.currentThread().isInterrupted())  // 任务被取消
                        System.out.println("PrimerTask.call： 你取消我干啥？");
                        return false;
                    
                    if (num % i == 0) 
                        return false;
                     else if (i % 100000000 == 0) 
                        System.out.print("i=" + i + "  ");
                        if (i % 600000000 == 0) 
                            System.out.println("\\n");
                        
                    
                
                return true;
            
        );
        threadPool.shutdown(); // 发送关闭线程池的指令
        cancelTask(future, 2000); //2秒后取消任务

        try 
            boolean is = future.get();
            System.out.println("--------------------------------------------is:" + is + "-----------------------");
         catch (CancellationException ex) 
            System.err.println("\\n\\n\\n任务被取消\\n\\n\\n");
         catch (InterruptedException ex) 
            System.err.println("当前线程被中断");
         catch (ExecutionException ex) 
            System.err.println("任务执行出错");
        


    


    private static void cancelTask(Future<?> future, int delay) 
        new Thread(new Runnable() 
            @Override
            public void run() 
                try 
                    Thread.sleep(delay);
                    future.cancel(true); // 取消与 future 关联的正在运行的任务
                 catch (InterruptedException ex) 
                    ex.printStackTrace(System.err);
                
            
        ).start();
    

看下运行效果：