定时器设计

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
		);
		
	}

}