java并发编程 - 8 - Future

java并发编程- 7 - 线程池这一章我们已经提到过Future，用于接收子线程的返回值。再来回顾一下代码：

@Test
    public void futureTest() throws ExecutionException, InterruptedException {
        // 创建 FutureTask
        FutureTask<User> futureTask = new FutureTask<User>(()-> {
                    return new User(2222,1000);
        });
        // 创建线程池
        ThreadPoolExecutor es=new ThreadPoolExecutor(20,50,3, TimeUnit.SECONDS,
                new ArrayBlockingQueue<>(200),new ThreadPoolExecutor.DiscardOldestPolicy());
        // 提交 FutureTask
        es.submit(futureTask);
        // 获取计算结果
        User result = futureTask.get();
        log.info("result:"+result);

    }

这个列子稍微有些简单，我们还是回到组装车子的场景：1、制造车身。2、制造轮子。3、制造车子。

(省略entity)代码如下：

 @Test
    public void madeCarUseFuture() throws ExecutionException, InterruptedException {
        //制造body
        FutureTask<CarBody> carBodyFutureTask=new FutureTask<CarBody>(new Callable<CarBody>() {
            @Override
            public CarBody call() throws Exception {
                log.info("madde body start");
                CarBody body=new CarBody("my carbody");
                Thread.sleep(2000);
                log.info("madde body success");
                return body;
            }
        });


        //制造轮子
        FutureTask<CarWheel> carWheelFutureTask=new FutureTask<CarWheel>(()->{
            log.info("made wheel start");
            CarWheel wheel=new CarWheel("my carWheel");
            Thread.sleep(2000);
            log.info("made wheel success");
            return wheel;
        });


        carBodyFutureTask.run();
        carWheelFutureTask.run();

        CarBody carBody=carBodyFutureTask.get();
        CarWheel wheel=carWheelFutureTask.get();

        //制造车子
        Car car=new Car(carBody,wheel);

        //从结果看出来，是同步执行的
        log.info(car.toString());

    }

    @Test
    public void madeCarUseFuturePool() throws ExecutionException, InterruptedException {

        ThreadPoolExecutor executor=new ThreadPoolExecutor(20,50,3, TimeUnit.SECONDS,
                new ArrayBlockingQueue<>(200),new ThreadPoolExecutor.DiscardOldestPolicy());

        //制造body

        FutureTask<CarBody> carBodyFutureTask=new FutureTask<CarBody>(new Callable<CarBody>() {
            @Override
            public CarBody call() throws Exception {
                log.info("madde body start");
                CarBody body=new CarBody("my carbody");
                Thread.sleep(2000);
                log.info("madde body success");
                return body;
            }
        });


        //制造轮子
        FutureTask<CarWheel> carWheelFutureTask=new FutureTask<CarWheel>(()->{
            log.info("made wheel start");
            CarWheel wheel=new CarWheel("my carWheel");
            Thread.sleep(2000);
            log.info("made wheel success");
            return wheel;
        });
        executor.submit(carBodyFutureTask);
        executor.submit(carWheelFutureTask);


        CarBody carBody=carBodyFutureTask.get();
        CarWheel wheel=carWheelFutureTask.get();

        //制造车子
        Car car=new Car(carBody,wheel);

        //从结果看出来，是异步执行的
        log.info(car.toString());

    }

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