一个java定时器框架

ScheduleIterator接口

import java.util.Date;

public interface ScheduleIterator 
{
    public Date next();//获取下一个触发的时间点
}

Scheduler类

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


public class Scheduler 
{
    class SchedulerTimerTask extends TimerTask 
    {
        private SchedulerTask schedulerTask;
        private ScheduleIterator iterator;
        public SchedulerTimerTask(SchedulerTask schedulerTask,ScheduleIterator iterator)
        {
            this.schedulerTask = schedulerTask;
            this.iterator = iterator;
        }
        public void run() 
        {
            schedulerTask.run();
            reschedule(schedulerTask, iterator);
        }
    }

    private final Timer timer = new Timer();

    public Scheduler() 
    {
    }
    public void cancel() 
    {
        timer.cancel();
    }
    public void schedule(SchedulerTask schedulerTask,ScheduleIterator iterator) 
    {
        Date time = iterator.next();
        if (time == null) 
        {
            schedulerTask.cancel();
        }
        else 
        {
            synchronized(schedulerTask.lock)
            {
                if (schedulerTask.state != SchedulerTask.VIRGIN) 
                {
                    throw new IllegalStateException("Task already scheduled " +
                        "or cancelled");
                }
                schedulerTask.state = SchedulerTask.SCHEDULED;
                schedulerTask.timerTask = new SchedulerTimerTask(schedulerTask, iterator);
                timer.schedule(schedulerTask.timerTask, time);
            }
        }
    }

    private void reschedule(SchedulerTask schedulerTask,ScheduleIterator iterator)
    {
        Date time = iterator.next();
        if (time == null)
        {
            schedulerTask.cancel();
        } 
        else 
        {
            synchronized(schedulerTask.lock)
            {
                if (schedulerTask.state != SchedulerTask.CANCELLED) 
                {
                    schedulerTask.timerTask = new SchedulerTimerTask(schedulerTask, iterator);
                    timer.schedule(schedulerTask.timerTask, time);
                }
            }
        }
    }
}

SchedulerTask 类

import java.util.TimerTask;

public abstract class SchedulerTask implements Runnable 
{//被调度器不断调度执行的任务

    final Object lock = new Object();

    int state = VIRGIN;//任务状态
    static final int VIRGIN = 0;
    static final int SCHEDULED = 1;
    static final int CANCELLED = 2;

    TimerTask timerTask;//底层的定时器任务
    protected SchedulerTask() 
    {
    }
    public abstract void run();//调度任务执行的具体任务
    public boolean cancel() 
    {
        synchronized(lock) 
        {
            if (timerTask != null) 
            {
                timerTask.cancel();//取消任务
            }
            boolean result = (state == SCHEDULED);//任务已经被调度执行
            state = CANCELLED;//设置任务状态为“取消”
            return result;
        }
    }
    public long scheduledExecutionTime()
    {
        synchronized(lock) 
        {
            return timerTask == null ? 0 : timerTask.scheduledExecutionTime();//任务执行时间
        }
    }

}

DailyIterator类：

import java.util.Calendar;
import java.util.Date;

public class DailyIterator implements ScheduleIterator {
    private final int hourOfDay, minute, second;
    private final Calendar calendar = Calendar.getInstance();

    public DailyIterator(int hourOfDay, int minute, int second)
    {
        this(hourOfDay, minute, second, new Date());
    }

    public DailyIterator(int hourOfDay, int minute, int second, Date date)
    {
        this.hourOfDay = hourOfDay;
        this.minute = minute;
        this.second = second;
        calendar.setTime(date);
        calendar.set(Calendar.HOUR_OF_DAY, hourOfDay);
        calendar.set(Calendar.MINUTE, minute);
        calendar.set(Calendar.SECOND, second);
        calendar.set(Calendar.MILLISECOND, 0);
        if (!calendar.getTime().before(date)) 
        {
            calendar.add(Calendar.DATE, -1);
        }
    }

    public Date next()
    {//获取下一个触发的时间点
        calendar.add(Calendar.DATE, 1);
        return calendar.getTime();
    }

}

测试类：

import java.text.SimpleDateFormat;

import java.util.Date;

import org.tiling.scheduling.Scheduler;
import org.tiling.scheduling.SchedulerTask;
import org.tiling.scheduling.examples.iterators.DailyIterator;

public class AlarmClock 
{

    private final Scheduler scheduler = new Scheduler();//调度器
    private final SimpleDateFormat dateFormat =
        new SimpleDateFormat("dd MMM yyyy HH:mm:ss.SSS");
    private final int hourOfDay, minute, second;//每天触发的时间点 

    public AlarmClock(int hourOfDay, int minute, int second) 
    {
        this.hourOfDay = hourOfDay;
        this.minute = minute;
        this.second = second;
    }

    public void start() 
    {
        scheduler.schedule(new SchedulerTask() 
        {
            public void run() 
            {
                soundAlarm();
            }
            private void soundAlarm()
            {
                System.out.println("Wake up! " +
                    "It's " + dateFormat.format(new Date()));
                // Start a new thread to sound an alarm
            }
        }, new DailyIterator(hourOfDay, minute, second));//通过迭代器模式迭代遍历得到后面一系列的时间点
    }

    public static void main(String[] args) 
    {
        AlarmClock alarmClock = new AlarmClock(22, 5, 0);
        alarmClock.start();
    }
}

参考资料

Scheduling recurring tasks in Java applications