public class Timer {
    //默認給線程命名："Timer-" + serialNumber()
	public Timer() {
        this("Timer-" + serialNumber());
    }
    //指定Timer的名字
    public Timer(String name) {
        thread.setName(name);
        thread.start();
    }
    //isDaemon：是否為守護線程
    public Timer(boolean isDaemon) {
        this("Timer-" + serialNumber(), isDaemon);
    }
    //給定線程名字，守護線程與否
    public Timer(String name, boolean isDaemon) {
        thread.setName(name);
        //setDaemon是指定線程是否為守護線程，true是守護線程，當(dāng)主線程退出，      守護線程退出
        thread.setDaemon(isDaemon);
        thread.start();
    }    
}
//TimerThread類 繼承Thread
class TimerThread extends Thread{
	private void mainLoop() {
	......
	//每次執(zhí)行下標為1的TimerTask
	task = queue.getMin();
	......
	}
}
//TaskQueue 類
class TaskQueue {
	//TaskQueue 中存儲TimerTask
    private TimerTask[] queue = new TimerTask[128];
    //返回數(shù)組中下標1的TimerTask
    TimerTask getMin() {
        return queue[1];
    }
}

public class TimerDemo {
	//指定Timer為守護線程，run方法結(jié)束Timer線程會結(jié)束。
    private static Timer timer = new Timer(true);
    //TimerTask 具體的定時任務(wù)
    static public class MyTask extends TimerTask {
        @Override
        public void run() {
            System.out.println("已運行，時間為：" + new Date());
        }
    }
    public static void main(String[] args) {
    	//創(chuàng)建定時任務(wù)
        MyTask myTask = new MyTask();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        //早于當(dāng)前時間，定時任務(wù)會立即執(zhí)行
        String dateString = "2020-06-01 09:56:00";
        try {
            Date taskDate = sdf.parse(dateString);
            //啟動定時任務(wù)
            timer.schedule(myTask,taskDate);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

public class TimerDemo {
    private static Timer timer = new Timer();
    static public class MyTaskA extends TimerTask {
        @Override
        public void run() {
        	//只輸出一次，MyTaskA 任務(wù)將會移除
            System.out.println("MyTaskA已運行，時間為：" + new Date());
            //執(zhí)行TimerTask的cancel方法，將自身任務(wù)從隊列中移除
            this.cancel();
        }
    }
    static public class MyTaskB extends TimerTask {
        @Override
        public void run() {
        	//移除MyTaskA任務(wù)，MyTaskB 任務(wù)不受影響
            System.out.println("MyTaskB已運行，時間為：" + new Date());
        }
    }
    public static void main(String[] args) {
        MyTaskA myTaskA = new MyTaskA();
        MyTaskB myTaskB = new MyTaskB();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String dateString = "2020-07-01 15:19:00";
        try {
            Date taskDate = sdf.parse(dateString);
            timer.schedule(myTaskA,taskDate,2000);
            timer.schedule(myTaskB,taskDate,2000);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

public class TimerDemo {
    private static Timer timer = new Timer();
    static public class MyTaskA extends TimerTask {
        @Override
        public void run() {
            System.out.println("MyTaskA已運行，時間為：" + new Date());
            //執(zhí)行Timer類的cancel方法，將Timer中所有任務(wù)從隊列中移除
            timer.cancel();
        }
    }
    static public class MyTaskB extends TimerTask {
        @Override
        public void run() {
            //MyTaskB也會被移除，因為MyTaskA與MyTaskB是隊列執(zhí)行，先執(zhí)行MyTaskA再執(zhí)行MyTaskB
            //MyTaskA中走了timer.cancel()，所以MyTaskB不會執(zhí)行
            System.out.println("MyTaskB已運行，時間為：" + new Date());
        }
    }
    public static void main(String[] args) {
        MyTaskA myTaskA = new MyTaskA();
        MyTaskB myTaskB = new MyTaskB();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String dateString = "2020-07-01 15:19:00";
        try {
            Date taskDate = sdf.parse(dateString);
            timer.schedule(myTaskA,taskDate,2000);
            timer.schedule(myTaskB,taskDate,2000);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

public void cancel() {
        synchronized(queue) {
            thread.newTasksMayBeScheduled = false;
            queue.clear();
            queue.notify();  // In case queue was already empty.
        }
    }

public class TimerDemo {
    private static Timer timer = new Timer();
    static public class MyTaskA extends TimerTask {
        @Override
        public void run() {
            System.out.println("MyTaskA已運行，時間為：" + new Date());
            try {
                //任務(wù)執(zhí)行時間是1s
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("MyTaskA已結(jié)束，時間為：" + new Date());
        }
    }
    public static void main(String[] args) {
        MyTaskA myTaskA = new MyTaskA();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String dateString = "2020-07-02 14:31:00";
        try {
            Date taskDate = sdf.parse(dateString);
            //3s執(zhí)行一次任務(wù)
            timer.scheduleAtFixedRate(myTaskA,taskDate,3000);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}