转：定时器设计

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1、传统的定时器实现

 

package cn.itcast.thread;

import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

public class TraditionalTimer {

    private static  int count = 0;

    public static void main(String[] args) {

        //延迟2秒执行run方法中的内容
        final Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            public void run() {
                System.out.println("haha");
            }
        }, 2000);

        //延迟2秒执行run方法中的内容，以后每间隔一秒去执行run方法
        timer.schedule(
                new TimerTask() {
                    public void run() {
                        System.out.println("hello java");
                    }
                },
                2000,
                1000);

        //延迟2秒执行run方法中的内容，以后根据count的值判断是间隔2秒还是4秒去执行run方法
        System.out.println(new Date().getSeconds());
        class MyTimerTask extends TimerTask {
            public void run() {
                count ++;
                System.out.println(new Date().getSeconds());
                System.out.println("hello java!");
                if (count % 2 == 1) {
                    timer.schedule(new MyTimerTask(), 4000);
                } else {
                    timer.schedule(new MyTimerTask(), 2000);
                }

            }
        }
        TimerTask tt = new MyTimerTask();
        timer.schedule(tt, 2000);
    }

}

2、利用jdk新特性来设计定时器

 

package cn.itcast.thread;

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

public class ModernTimerTest {

    public static void main(String[] args) {

        final ScheduledExecutorService timer = Executors.newScheduledThreadPool(1);
        timer.schedule(
                new Runnable() {
                    public void run() {
                        System.out.println(Calendar.getInstance().get(Calendar.SECOND));
                    }
                },
        1,
        TimeUnit.SECONDS
        );

        class MyTask implements Runnable {
            public void run() {
                System.out.println(" ----> " + Calendar.getInstance().get(Calendar.SECOND));
                timer.schedule(new MyTask(), 2, TimeUnit.SECONDS);
            }
        }

        timer.schedule(
                new MyTask(),
                1,
                TimeUnit.SECONDS
        );

    }

}