在應(yīng)用開發(fā)中，經(jīng)常需要一些周期性的操作，比如每5分鐘檢查一下新郵件等。對于這樣的操作最方便、高效的實現(xiàn)方式就是使用java.util.Timer工具類。比如下面的代碼每5分鐘檢查一遍是否有新郵件：
package?test.Timer;

import?java.util.Timer;
import?java.util.TimerTask;

public?class?EngeeTimer?{

????private?int?minutes;

????private?Timer?timer?=?new?Timer();

????public?int?getMinutes()?{
????????return?minutes;
????}

????public?void?setMinutes(int?minutes)?{
????????this.minutes?=?minutes;
????}

????public?void?start()?{

????????timer.schedule(new?TimerTask()?{

????????????public?void?run()?{
????????????????System.out.print("接受郵件");

????????????}

????????},?0,?minutes?*?1000?*?60);

????}

????public?Timer?getTimer()?{
????????return?timer;
????}

????public?void?setTimer(Timer?timer)?{
????????this.timer?=?timer;
????}

}

　　使用這幾行代碼之后，Timer本身會每隔5分鐘調(diào)用一遍server.checkNewMail()方法，不需要自己啟動線程。Timer本身也是多線程同步的，多個線程可以共用一個Timer，不需要外部的同步代碼。
在《The JavaTutorial》中有更完整的例子：

?1package?test.Timer;
?2
?3public?class?Main?{
?4
?5????
?6????public?static?void?main(String[]?args)?{
?7????????EngeeTimer?entimer=new?EngeeTimer();
?8????????entimer.setMinutes(1);
?9????????entimer.start();
10
11????}
12
13}
14

運行結(jié)果：
３分鐘后
hahaha,this is a timenrhahaha,this is a timenrhahaha,this is a timenrhahaha,this is a timenrhahaha,th