timer.java

一个应用timer的小程序

package net.sujee.javatimer;

import java.util.Vector;
import net.sujee.javatimer.TimerCallback;

public class Timer extends Thread
{
   Vector mCallbacks;
   boolean mKeepWorking;
   long mNotifyTicks;

   public static final int DEFAULT_TICK_INTERVAL = 1000; // 1 sec

   public Timer ()
   {
      super ("Timer thread");
      mCallbacks = new Vector ();
      mKeepWorking = true;
      mNotifyTicks = DEFAULT_TICK_INTERVAL; // one Sec default

      start();
   }

   public synchronized void addCallback (TimerCallback callback,
   		long tickInterval)
   {
      if (callback != null)
      {
         Callback client = new Callback ();
         client.callback = callback;
         client.tickInterval = (tickInterval > 0) ? tickInterval : DEFAULT_TICK_INTERVAL;
         mCallbacks.add (client);

         // also modify the maximum time I should sleep
         if ( client.tickInterval < mNotifyTicks)
            mNotifyTicks = client.tickInterval;
      }
   }

   public synchronized void removeCallback (TimerCallback callback)
   {
      int totalCallbacks = mCallbacks.size();
      for (int i=0 ; i<  totalCallbacks ; ++i)
      {
         Callback c = (Callback) mCallbacks.get(i);
         if (c.callback == callback)
         {
            mCallbacks.remove(i);
            return;
         }
      }
   }

   public void stopTicking ()
   {
      mKeepWorking = false;
   }

   public void run ()
   {
      long lastTime = System.currentTimeMillis();
      while (mKeepWorking)
      {
         synchronized (this)
         {
            if ( (System.currentTimeMillis()-lastTime) >= mNotifyTicks )
            {
               int callbackCount = mCallbacks.size();
               for (int i=0; i < callbackCount; ++i)
               {
                  Callback c = (Callback) mCallbacks.get(i);
                  long elapsedTime = System.currentTimeMillis() -c.lastNotified;
                  if ( c.tickInterval <= elapsedTime)
                  {
                     c.callback.tick ();
                     c.lastNotified = System.currentTimeMillis();
                   }
               }
               lastTime = System.currentTimeMillis();
            }
         }

         // now sleep for a while!
         try
         {
            sleep (mNotifyTicks/2);
         }
         catch (InterruptedException e)
         {
            // no need to do anytihng
         }
      }
   }
}


class Callback
{
   long tickInterval;
   long lastNotified;
   TimerCallback callback;
}