java高级---->Thread之ScheduledExecutorService的使用

ScheduledExecutorService的主要作用就是可以将定时任务与线程池功能结合使用。今天我们来学习一下ScheduledExecutorService的用法。我们都太渺小了，那么容易便湮没于各自的殊途。

 
ScheduledExecutorService的简单使用

一、使用scheduleAtFixedRate()方法实现周期性执行
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public class ScheduledExecutorServiceTest {
    public static void main(String[] args) {
        ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
        executorService.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                System.out.println("run "+ System.currentTimeMillis());
            }
        }, 0, 100, TimeUnit.MILLISECONDS);
    }
}
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 运行的结果如下：立刻执行，而且每隔100毫秒执行一次。

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run 1501051231331
run 1501051231427
run 1501051231527
run 1501051231628
run 1501051231726
run 1501051231827
run 1501051231926
run 1501051232026
run 1501051232127
.......
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二、ScheduledExecutorService使用Callable延迟运行
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package com.linux.thread;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;

public class CallableRun {
    public static void main(String[] args) {
        try {
            List<Callable> callableList = new ArrayList<>();
            callableList.add(new MyCallableA());
            callableList.add(new MyCallableB());
            ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
            ScheduledFuture futureA = executorService.schedule(callableList.get(0), 4L, TimeUnit.SECONDS);
            ScheduledFuture futureB = executorService.schedule(callableList.get(1), 4L, TimeUnit.SECONDS);

            System.out.println("            X = " + System.currentTimeMillis());
            System.out.println("返回值A：" + futureA.get());
            System.out.println("返回值B：" + futureB.get());
            System.out.println("            Y = " + System.currentTimeMillis());

            executorService.shutdown();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }

    static class MyCallableA implements Callable<String> {
        @Override
        public String call() throws Exception{
            try {
                System.out.println("callA begin " + Thread.currentThread().getName() + ", " + System.currentTimeMillis());
                TimeUnit.SECONDS.sleep(3); // 休眠3秒
                System.out.println("callA end " + Thread.currentThread().getName() + ", " + System.currentTimeMillis());
            } catch (Exception e) {
                e.printStackTrace();
            }
            return "returnA";
        }
    }

    static class MyCallableB implements Callable<String>  {
        @Override
        public String call() throws Exception{
            System.out.println("callB begin " + Thread.currentThread().getName() + ", " + System.currentTimeMillis());
            System.out.println("callB end " + Thread.currentThread().getName() + ", " + System.currentTimeMillis());
            return "returnB";
        }
    }
}
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运行的结果如下：



 

三、使用scheduleWithFixedDelay()方法实现周期性执行
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package com.linux.thread;

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class RunMain {
    public static void main(String[] args) {
        ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
        System.out.println("          x = " + System.currentTimeMillis());
        executorService.scheduleWithFixedDelay(new MyRunable(), 1, 2, TimeUnit.SECONDS);
        System.out.println("          y = " + System.currentTimeMillis());
    }

    static class MyRunable implements Runnable {
        @Override
        public void run() {
            try {
                System.out.println("     begin = " + System.currentTimeMillis() + ", name: " + Thread.currentThread().getName());
                TimeUnit.SECONDS.sleep(4);
                System.out.println("     end = " + System.currentTimeMillis() + ", name: " + Thread.currentThread().getName());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}
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运行的结果如下：