首先看一下jdk自带定时器：

一种工具，线程用其安排以后在后台线程中执行的任务。可安排任务执行一次，或者定期重复执行。与每个 Timer 对象相对应的是单个后台线程，用于顺序地执行所有计时器任务。计时器任务应该迅速完成。如果完成某个计时器任务的时间太长，那么它会“独占”计时器的任务执行线程。因此，这就可能延迟后续任务的执行，而这些任务就可能“堆在一起”，并且在上述不友好的任务最终完成时才能够被快速连续地执行。

schedule(TimerTask task,long delay) 安排在指定延迟后执行指定的任务。
schedule(TimerTask task,Date time) 安排在指定的时间执行指定的任务。如果此时间已过去，则安排立即执行该任务。
schedule(TimerTask task, long delay, long period) 安排指定的任务从指定的延迟后开始进行重复的固定延迟执行。如果由于任何原因（如垃圾回收或其他后台活动）而延迟了某次执行，则后续执行也将被延迟
schedule(TimerTask task,Date firstTime,long period) 安排指定的任务在指定的时间开始进行重复的固定延迟执行。如果由于任何原因（如垃圾回收或其他后台活动）而延迟了某次执行，则后续执行也将被延迟。

package test;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Date;import java.util.Timer;import java.util.TimerTask;/** * jdk自带定时器 * * @author LIUTIE * */public class JDKTimer { public static void main(String[] args) throws ParseException { //日期格式工具 final SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); Timer timer = new Timer(); // 10s后执行定时器，仅执行一次 System.out.print(sdf.format(new Date())); System.out.println("the timer one will be executed after 10 seconds..."); long milliseconds = 10 * 1000; timer.schedule(new TimerTask() { @Override public void run() { System.out.print(sdf.format(new Date())); System.out.println("the timer one has finished execution"); } }, milliseconds); //12秒后执行定时器，每1s执行一次 System.out.print(sdf.format(new Date())); System.out.println("the timer two will be executed after 12 seconds..."); //启动后延迟时间 long afterSs = 12 * 1000; //执行周期 long intervalSs1 = 1 * 1000; timer.schedule(new TimerTask() { // 执行计数器 int i = 0; @Override public void run() { System.out.print(sdf.format(new Date())); System.out.println("the timer two has execution " + (++i) + " timers"); // 执行10次后关闭定时器 if (i == 10) { this.cancel(); } } }, afterSs, intervalSs1); // 指定时间执行定时器，仅执行一次 System.out.print(sdf.format(new Date())); System.out.println("the timer three will be executed at 2017-06-27 21:47:00..."); Date date = sdf.parse("2017-06-27 21:47:00"); timer.schedule(new TimerTask() { @Override public void run() { System.out.print(sdf.format(new Date())); System.out.println("the timer three has finished execution"); } }, date); // 从指定时间开始周期性执行 System.out.print(sdf.format(new Date())); System.out.println("the timer four will be executed at 2017-06-27 21:48:00..."); // 执行间隔周期 long intervalSs = 1 * 1000; // 开始执行时间 Date beginTime = sdf.parse("2017-06-27 21:48:00"); timer.schedule(new TimerTask() { // 执行计数器 int i = 0; @Override public void run() { System.out.print(sdf.format(new Date())); System.out.println("the timer four has execution " + (++i) + " timers"); // 执行10次后关闭定时器 if (i == 10) { this.cancel(); } } }, beginTime, intervalSs); }}

执行结果

2017-06-27 21:46:24the timer one will be executed after 10 seconds...2017-06-27 21:46:24the timer two will be executed after 12 seconds...2017-06-27 21:46:24the timer three will be executed at 2017-06-27 21:47:00...2017-06-27 21:46:24the timer four will be executed at 2017-06-27 21:48:00...2017-06-27 21:46:34the timer one has finished execution2017-06-27 21:46:36the timer two has execution 1 timers2017-06-27 21:46:37the timer two has execution 2 timers2017-06-27 21:46:38the timer two has execution 3 timers2017-06-27 21:46:39the timer two has execution 4 timers2017-06-27 21:46:40the timer two has execution 5 timers2017-06-27 21:46:41the timer two has execution 6 timers2017-06-27 21:46:42the timer two has execution 7 timers2017-06-27 21:46:43the timer two has execution 8 timers2017-06-27 21:46:44the timer two has execution 9 timers2017-06-27 21:46:45the timer two has execution 10 timers2017-06-27 21:47:00the timer three has finished execution2017-06-27 21:48:00the timer four has execution 1 timers2017-06-27 21:48:01the timer four has execution 2 timers2017-06-27 21:48:02the timer four has execution 3 timers2017-06-27 21:48:03the timer four has execution 4 timers2017-06-27 21:48:04the timer four has execution 5 timers2017-06-27 21:48:05the timer four has execution 6 timers2017-06-27 21:48:06the timer four has execution 7 timers2017-06-27 21:48:07the timer four has execution 8 timers2017-06-27 21:48:08the timer four has execution 9 timers2017-06-27 21:48:09the timer four has execution 10 timers

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