jdk中的定时器

Posted 2020-09-25

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。

 1 package test;
 2 
 3 import java.text.ParseException;
 4 import java.text.SimpleDateFormat;
 5 import java.util.Date;
 6 import java.util.Timer;
 7 import java.util.TimerTask;
 8 
 9 /**
10  * jdk自带定时器
11  * 
12  * @author LIUTIE
13  *
14  */
15 public class JDKTimer {
16     
17 
18     public static void main(String[] args) throws ParseException {
19         //日期格式工具
20         final SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
21         
22         Timer timer = new Timer();
23         // 10s后执行定时器，仅执行一次
24         System.out.print(sdf.format(new Date()));
25         System.out.println("the timer one will be executed after 10 seconds...");
26         long milliseconds = 10 * 1000;
27         timer.schedule(new TimerTask() {
28 
29             @Override
30             public void run() {
31                 System.out.print(sdf.format(new Date()));
32                 System.out.println("the timer one has finished execution");
33             }
34         }, milliseconds);
35         
36         //12秒后执行定时器，每1s执行一次
37         System.out.print(sdf.format(new Date()));
38         System.out.println("the timer two will be executed after 12 seconds...");
39         //启动后延迟时间
40         long afterSs = 12 * 1000;
41         //执行周期
42         long intervalSs1 = 1 * 1000;
43         timer.schedule(new TimerTask() {
44             // 执行计数器
45             int i = 0;
46 
47             @Override
48             public void run() {
49                 System.out.print(sdf.format(new Date()));
50                 System.out.println("the timer two has execution " + (++i) + " timers");
51                 // 执行10次后关闭定时器
52                 if (i == 10) {
53                     this.cancel();
54                 }
55             }
56         }, afterSs, intervalSs1);
57         
58         
59         // 指定时间执行定时器，仅执行一次
60         System.out.print(sdf.format(new Date()));
61         System.out.println("the timer three will be executed at 2017-06-27 21:47:00...");
62         Date date = sdf.parse("2017-06-27 21:47:00");
63         timer.schedule(new TimerTask() {
64 
65             @Override
66             public void run() {
67                 System.out.print(sdf.format(new Date()));
68                 System.out.println("the timer three has finished execution");
69             }
70         }, date);
71         
72         // 从指定时间开始周期性执行
73         System.out.print(sdf.format(new Date()));
74         System.out.println("the timer four will be executed at 2017-06-27 21:48:00...");
75         // 执行间隔周期
76         long intervalSs = 1 * 1000;
77         // 开始执行时间
78         Date beginTime = sdf.parse("2017-06-27 21:48:00");
79         timer.schedule(new TimerTask() {
80             // 执行计数器
81             int i = 0;
82 
83             @Override
84             public void run() {
85                 System.out.print(sdf.format(new Date()));
86                 System.out.println("the timer four has execution " + (++i) + " timers");
87                 // 执行10次后关闭定时器
88                 if (i == 10) {
89                     this.cancel();
90                 }
91             }
92         }, beginTime, intervalSs);
93     }
94 
95 }

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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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