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TimerQueue.java
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1998-06-30
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/*
* @(#)TimerQueue.java 1.21 98/06/08
*
* Copyright 1997, 1998 by Sun Microsystems, Inc.,
* 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
* All rights reserved.
*
* This software is the confidential and proprietary information
* of Sun Microsystems, Inc. ("Confidential Information"). You
* shall not disclose such Confidential Information and shall use
* it only in accordance with the terms of the license agreement
* you entered into with Sun.
*/
/**
* Internal class to manage all Timers using one thread.
*
*
* @version 1.21 06/08/98
* @author Dave Moore
*/
package com.sun.java.swing;
import java.util.*;
/** Private class to manage a queue of Timers. The Timers are chained
* together in a linked list sorted by the order in which they will expire.
*/
class TimerQueue implements Runnable {
Timer firstTimer;
boolean running;
private static final Object sharedInstanceKey = new StringBuffer("TimerQueue.sharedInstanceKey");
private static final Object expiredTimersKey = new StringBuffer("TimerQueue.expiredTimersKey");
public TimerQueue() {
super();
// Now start the TimerQueue thread.
start();
}
public static TimerQueue sharedInstance() {
synchronized (TimerQueue.class) {
TimerQueue sharedInst = (TimerQueue)
SwingUtilities.appContextGet(sharedInstanceKey);
if (sharedInst == null) {
sharedInst = new TimerQueue();
SwingUtilities.appContextPut(sharedInstanceKey,
sharedInst);
}
return sharedInst;
}
}
synchronized void start() {
if (running) {
throw new RuntimeException("Can't start a TimerQueue that is already running");
} else {
Thread timerThread = new Thread(this, "TimerQueue");
try {
timerThread.setDaemon(true);
} catch (SecurityException e) {
}
timerThread.start();
running = true;
}
}
synchronized void stop() {
running = false;
notify();
}
synchronized void addTimer(Timer timer, long expirationTime) {
Timer previousTimer, nextTimer;
// If the Timer is already in the queue, then ignore the add.
if (timer.running) {
return;
}
previousTimer = null;
nextTimer = firstTimer;
// Insert the Timer into the linked list in the order they will
// expire. If two timers expire at the same time, put the newer entry
// later so they expire in the order they came in.
while (nextTimer != null) {
if (nextTimer.expirationTime > expirationTime)
break;
previousTimer = nextTimer;
nextTimer = nextTimer.nextTimer;
}
if (previousTimer == null)
firstTimer = timer;
else
previousTimer.nextTimer = timer;
timer.expirationTime = expirationTime;
timer.nextTimer = nextTimer;
timer.running = true;
notify();
}
synchronized void removeTimer(Timer timer) {
boolean found;
Timer previousTimer, nextTimer;
if (!timer.running)
return;
previousTimer = null;
nextTimer = firstTimer;
found = false;
while (nextTimer != null) {
if (nextTimer == timer) {
found = true;
break;
}
previousTimer = nextTimer;
nextTimer = nextTimer.nextTimer;
}
if (!found)
return;
if (previousTimer == null)
firstTimer = timer.nextTimer;
else
previousTimer.nextTimer = timer.nextTimer;
timer.expirationTime = 0;
timer.nextTimer = null;
timer.running = false;
}
synchronized boolean containsTimer(Timer timer) {
return timer.running;
}
// If there are a ton of timers, this method may never return. It loops
// checking to see if the head of the Timer list has expired. If it has,
// it posts the Timer and reschedules it if necessary.
synchronized long postExpiredTimers() {
long currentTime, timeToWait;
Timer timer;
// The timeToWait we return should never be negative and only be zero
// when we have no Timers to wait for.
do {
timer = firstTimer;
if (timer == null)
return 0;
currentTime = System.currentTimeMillis();
timeToWait = timer.expirationTime - currentTime;
if (timeToWait <= 0) {
try {
timer.post(); // have timer post an event
} catch (SecurityException e) {}
// remove the timer from the queue
removeTimer(timer);
// This tries to keep the interval uniform at the cost of
// drift.
if (timer.isRepeats()) {
addTimer(timer, currentTime + timer.getDelay());
}
}
// Allow other threads to call addTimer() and removeTimer()
// even when we are posting Timers like mad. Since the wait()
// releases the lock, be sure not to maintain any state
// between iterations of the loop.
try {
wait(1);
} catch (InterruptedException e) {
}
} while (timeToWait <= 0);
return timeToWait;
}
public synchronized void run() {
long timeToWait;
try {
while (running) {
timeToWait = postExpiredTimers();
try {
wait(timeToWait);
}
catch (InterruptedException e) { }
}
}
catch (ThreadDeath td) {
running = false;
// Mark all the timers we contain as not being queued.
Timer timer = firstTimer;
while(timer != null) {
timer.eventQueued = false;
timer = timer.nextTimer;
}
SystemEventQueueUtilities.restartTimerQueueThread();
throw td;
}
}
public synchronized String toString() {
StringBuffer buf;
Timer nextTimer;
buf = new StringBuffer();
buf.append("TimerQueue (");
nextTimer = firstTimer;
while (nextTimer != null) {
buf.append(nextTimer.toString());
nextTimer = nextTimer.nextTimer;
if (nextTimer != null)
buf.append(", ");
}
buf.append(")");
return buf.toString();
}
}