jdk自带定时器使用方法详解

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 execution
2017-06-27 21:46:36the timer two has execution 1 timers
2017-06-27 21:46:37the timer two has execution 2 timers
2017-06-27 21:46:38the timer two has execution 3 timers
2017-06-27 21:46:39the timer two has execution 4 timers
2017-06-27 21:46:40the timer two has execution 5 timers
2017-06-27 21:46:41the timer two has execution 6 timers
2017-06-27 21:46:42the timer two has execution 7 timers
2017-06-27 21:46:43the timer two has execution 8 timers
2017-06-27 21:46:44the timer two has execution 9 timers
2017-06-27 21:46:45the timer two has execution 10 timers
2017-06-27 21:47:00the timer three has finished execution
2017-06-27 21:48:00the timer four has execution 1 timers
2017-06-27 21:48:01the timer four has execution 2 timers
2017-06-27 21:48:02the timer four has execution 3 timers
2017-06-27 21:48:03the timer four has execution 4 timers
2017-06-27 21:48:04the timer four has execution 5 timers
2017-06-27 21:48:05the timer four has execution 6 timers
2017-06-27 21:48:06the timer four has execution 7 timers
2017-06-27 21:48:07the timer four has execution 8 timers
2017-06-27 21:48:08the timer four has execution 9 timers
2017-06-27 21:48:09the timer four has execution 10 timers

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