多线程 定时器 Timer TimerTask

定时器是一种特殊的多线程，使用Timer来安排一次或者重复执行某个任务

package org.zln.thread;

import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

/**
 * Created by coolkid on 2015/6/21 0021.
 */
public class TestTimerTask extends TimerTask {
    @Override
    public void run() {
        System.out.println(new Date());
    }

    public static void main(String[] args) {
        Timer timer = new Timer();
        TestTimerTask testTimerTask = new TestTimerTask();
        timer.schedule(testTimerTask,1000,1000);

    }
}

 Timer是一个定时容器，TimerTask子类是具体任务实现类

小练习：

　　间隔一分钟扫描某个目录下是否存在指定文件

package org.zln.thread;

import java.io.File;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

/**
 * Created by coolkid on 2015/6/21 0021.
 */
public class TestTimerTask extends TimerTask {

    private String path;
    private boolean flag = true;

    public TestTimerTask(String path) {
        this.path = path;
    }

    @Override
    public void run() {
        File file = new File(path);
        if (flag&&!file.isDirectory()&&file.exists()){
            System.out.println(new Date()+"已检测到文件");
            flag = false;
        }
        if (!flag){
            System.out.println(new Date()+"已经检测到文件，无需再次检测");
        }
        if (flag&&(file.isDirectory()||!file.exists())){
            System.out.println(new Date()+"未检测到文件");
        }
    }

    public static void main(String[] args) {
        Timer timer = new Timer();
        TestTimerTask testTimerTask = new TestTimerTask("E:\GitHub\tools\实用jar程序\创建或删除标识文件\zln.txt");
        timer.schedule(testTimerTask,1000,60000);

    }
}

其他常用Timer方法

　　

Modifier and Type	Method and Description
void	cancel() Terminates this timer, discarding any currently scheduled tasks.
int	purge() Removes all cancelled tasks from this timer's task queue.
void	schedule(TimerTask task, Date time) Schedules the specified task for execution at the specified time.
void	schedule(TimerTask task, Date firstTime, long period) Schedules the specified task for repeated fixed-delay execution, beginning at the specified time.
void	schedule(TimerTask task, long delay) Schedules the specified task for execution after the specified delay.
void	schedule(TimerTask task, long delay, long period) Schedules the specified task for repeated fixed-delay execution, beginning after the specified delay.
void	scheduleAtFixedRate(TimerTask task, Date firstTime, long period) Schedules the specified task for repeated fixed-rate execution, beginning at the specified time.
void	scheduleAtFixedRate(TimerTask task, long delay, long period) Schedules the specified task for repeated fixed-rate execution, beginning after the specified delay.