Java thread Timer timer

The timing/planning function mainly uses the Timer object, which still uses multi-threading for processing internally, so it is still very closely related to thread technology.

The main function of the Timer class is to set up scheduled tasks, but the class that encapsulates the task is the TimerTask class. TimerTask class is an abstract class.

The execution time of the task is later than the current time-----The effect of execution in the future

import java.util.Date;
import java.util.TimerTask;
 
public class MyTask extends TimerTask{
 
	@Override
	public void run() {
		System.out.println("任务执行了, 时间为:" + new Date());
	}
}
 
public class Test1 {
	public static void main(String[] args){
		System.out.println("当前时间为: " + new Date());
		Calendar calendarRef = Calendar.getInstance();
		calendarRef.add(Calendar.SECOND, 10);
		Date runDate = calendarRef.getTime();
		
		MyTask task = new MyTask();
        // 查看Timer构造方法,创建一个Timer就是启动一个新的线程
		Timer timer = new Timer();
		timer.schedule(task, runDate); // 定时器在某个时间(runDate)执行某个任务(task)
	}
}

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Timer allows multiple TimerTask tasks and delayed tests

TimerTask is executed sequentially one by one in a queue, so the execution time is It may not be consistent with the expected time, because the previous task may take a long time, and the running time of the subsequent task will also be delayed.

import java.util.Date;
import java.util.TimerTask;
 
public class MyTaskA extends TimerTask{
 
	@Override
	public void run() {
		try {
			System.out.println("A begin timer, 时间为:" + new Date());
			Thread.sleep(20000);
			System.out.println("A   end timer, 时间为:" + new Date());
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
}

import java.util.Date;
import java.util.TimerTask;
 
public class MyTaskB extends TimerTask{
 
	@Override
	public void run() {
		System.out.println("B begin timer, 时间为:" + new Date());
		System.out.println("B   end timer, 时间为:" + new Date());
	}
}
 
import java.util.Calendar;
import java.util.Date;
import java.util.Timer;
 
public class Test1 {
	public static void main(String[] args){
		System.out.println("当前时间为: " + new Date());
		Calendar calendarRef1 = Calendar.getInstance();
		Date runDate1 = calendarRef1.getTime();
		System.out.println("A计划时间为: " + runDate1);
		
		Calendar calendarRef2 = Calendar.getInstance();
		calendarRef2.add(Calendar.SECOND, 10);
		Date runDate2 = calendarRef2.getTime();
		System.out.println("B计划时间为: " + runDate2);
		
		MyTaskA task1 = new MyTaskA();
		MyTaskB task2 = new MyTaskB();
		Timer timer = new Timer();
		timer.schedule(task1, runDate1); // 定时器在某个时间(runDate)执行某个任务(task)
		timer.schedule(task2, runDate2);
	}
}

schedule(TimerTask task, Date firstTime, long period)

The function of this method is to execute in an infinite loop at the specified interval after the specified date a certain task.

import java.util.Date;
import java.util.TimerTask;
 
public class MyTask extends TimerTask{
 
	@Override
	public void run() {
		System.out.println("任务开始: "+new Date());
		System.out.println("mytask...");
		System.out.println("任务结束: "+new Date());
	}
}
 
import java.util.Calendar;
import java.util.Date;
import java.util.Timer;
 
public class Run {
	public static void main(String[] args){
		System.out.println("当前时间为:"+new Date());
		Calendar c = Calendar.getInstance();
		c.add(Calendar.SECOND, 10);
		Date runDate1 = c.getTime();
		System.out.println("计划时间为:"+runDate1);
		
		MyTask myTask = new MyTask();
		Timer timer = new Timer();
		timer.schedule(myTask, runDate1, 10000);
	}
}

The cancel() method of the TimerTask class

The function of the cancel() method in the TimerTask class is to clear itself from the task queue.

import java.util.Date;
import java.util.TimerTask;
 
public class MyTaskA extends TimerTask{
 
	@Override
	public void run() {
		System.out.println("A run timer="+new Date());
		this.cancel();
		System.out.println("A任务自己移除自己");
	}
}
 
import java.util.Date;
import java.util.TimerTask;
 
public class MyTaskB extends TimerTask{
 
	@Override
	public void run() {
		System.out.println("B run timer="+new Date());
	}
}
 
import java.util.Calendar;
import java.util.Date;
import java.util.Timer;
 
public class Run {
	public static void main(String[] args){
		System.out.println("当前时间为:"+new Date());
		Calendar c = Calendar.getInstance();
		Date runDate1 = c.getTime();
		System.out.println("计划时间为:"+runDate1);
		
		MyTaskA myTaskA = new MyTaskA();
		MyTaskB myTaskB = new MyTaskB();
		Timer timer = new Timer();
		timer.schedule(myTaskA, runDate1, 4000);
		timer.schedule(myTaskB, runDate1, 4000);
	}
}

Timer's cancel() method

Different from the cancel() method in the TimerTask class that clears itself, the cancel() method in the Timer class is to clear all the tasks in the task queue. The task is cleared.

import java.util.Date;
import java.util.TimerTask;
 
public class MyTaskA extends TimerTask{
 
	@Override
	public void run() {
		System.out.println("A run timer="+new Date());
		this.cancel();
		System.out.println("A任务自己移除自己");
	}
}
 
import java.util.Date;
import java.util.TimerTask;
 
public class MyTaskB extends TimerTask{
 
	@Override
	public void run() {
		System.out.println("B run timer="+new Date());
	}
}
 
import java.util.Calendar;
import java.util.Date;
import java.util.Timer;
 
public class Run {
	public static void main(String[] args){
		System.out.println("当前时间为:"+new Date());
		Calendar c = Calendar.getInstance();
		Date runDate1 = c.getTime();
		System.out.println("计划时间为:"+runDate1);
		
		MyTaskA myTaskA = new MyTaskA();
		MyTaskB myTaskB = new MyTaskB();
		Timer timer = new Timer();
		timer.schedule(myTaskA, runDate1, 4000);
		timer.schedule(myTaskB, runDate1, 4000);
	}
}

schedule(TimerTask task, long delay)

The function of this method is to use the current time when the schedule(TimerTask task, long delay) method is executed as the reference time. Execute a TimerTask task after delaying the specified number of milliseconds based on this time.

import java.util.Date;
import java.util.TimerTask;
 
public class MyTask extends TimerTask{
 
	@Override
	public void run() {
		System.out.println("A run timer="+new Date());
	}
}
 
import java.util.Calendar;
import java.util.Date;
import java.util.Timer;
 
public class Run {
	public static void main(String[] args) throws InterruptedException{
		System.out.println("当前时间为:"+new Date());
		Calendar c = Calendar.getInstance();
		Date runDate1 = c.getTime();
		System.out.println("计划时间为:"+runDate1);
		
		MyTask myTask = new MyTask();
		Timer timer = new Timer();
		timer.schedule(myTask, 7000); // 计划任务延迟7秒后执行
		Thread.sleep(10000);
		timer.cancel();
	}
}

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