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/*
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* Copyright (c) 1995, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.misc;
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/**
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A Timer object is used by algorithms that require timed events.
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For example, in an animation loop, a timer would help in
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determining when to change frames.
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A timer has an interval which determines when it "ticks";
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that is, a timer delays for the specified interval and then
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it calls the owner's tick() method.
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Here's an example of creating a timer with a 5 sec interval:
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<pre>
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class Main implements Timeable {
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public void tick(Timer timer) {
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System.out.println("tick");
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}
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public static void main(String args[]) {
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(new Timer(this, 5000)).cont();
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}
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}
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</pre>
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A timer can be stopped, continued, or reset at any time.
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A timer's state is not stopped while it's calling the
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owner's tick() method.
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A timer can be regular or irregular. If in regular mode,
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a timer ticks at the specified interval, regardless of
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how long the owner's tick() method takes. While the timer
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is running, no ticks are ever discarded. That means that if
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the owner's tick() method takes longer than the interval,
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the ticks that would have occurred are delivered immediately.
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In irregular mode, a timer starts delaying for exactly
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the specified interval only after the tick() method returns.
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Synchronization issues: do not hold the timer's monitor
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while calling any of the Timer operations below otherwise
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the Timer class will deadlock.
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@author Patrick Chan
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*/
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/*
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Synchronization issues: there are two data structures that
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require locking. A Timer object and the Timer queue
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(described in the TimerThread class). To avoid deadlock,
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the timer queue monitor is always acquired before the timer
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object's monitor. However, the timer queue monitor is acquired
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only if the timer operation will make use of the timer
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queue, e.g. stop().
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The class monitor on the class TimerThread severs as the monitor
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to the timer queue.
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Possible feature: perhaps a timer should have an associated
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thread priority. The thread that makes the callback temporarily
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takes on that priority before calling the owner's tick() method.
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*/
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public class Timer {
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/**
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* This is the owner of the timer. Its tick method is
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* called when the timer ticks.
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*/
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public Timeable owner;
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/*
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* This is the interval of time in ms.
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*/
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long interval;
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/*
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* This variable is used for two different purposes.
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* This is done in order to save space.
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* If 'stopped' is true, this variable holds the time
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* that the timer was stopped; otherwise, this variable
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* is used by the TimerThread to determine when the timer
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* should tick.
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*/
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long sleepUntil;
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/*
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* This is the time remaining before the timer ticks. It
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* is only valid if 'stopped' is true. If the timer is
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* continued, the next tick will happen remaingTime
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* milliseconds later.
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*/
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long remainingTime;
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/*
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* True iff the timer is in regular mode.
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*/
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boolean regular;
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/*
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* True iff the timer has been stopped.
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*/
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boolean stopped;
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/* **************************************************************
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* Timer queue-related variables
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* ************************************************************** */
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/*
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* A link to another timer object. This is used while the
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* timer object is enqueued in the timer queue.
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*/
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Timer next;
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/* **************************************************************
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* Timer methods
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* ************************************************************** */
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/*
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* This variable holds a handle to the TimerThread class for
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* the purpose of getting at the class monitor. The reason
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* why Class.forName("TimerThread") is not used is because it
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* doesn't appear to work when loaded via a net class loader.
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*/
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static TimerThread timerThread = null;
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/**
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* Creates a timer object that is owned by 'owner' and
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* with the interval 'interval' milliseconds. The new timer
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* object is stopped and is regular. getRemainingTime()
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* return 'interval' at this point. getStopTime() returns
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* the time this object was created.
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* @param owner owner of the timer object
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* @param interval interval of the timer in milliseconds
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*/
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public Timer(Timeable owner, long interval) {
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this.owner = owner;
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this.interval = interval;
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remainingTime = interval;
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regular = true;
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sleepUntil = System.currentTimeMillis();
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stopped = true;
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synchronized (getClass()) {
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if (timerThread == null) {
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timerThread = new TimerThread();
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}
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}
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}
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/**
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* Returns true if this timer is stopped.
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*/
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public synchronized boolean isStopped() {
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return stopped;
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}
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/**
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* Stops the timer. The amount of time the timer has already
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* delayed is saved so if the timer is continued, it will only
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* delay for the amount of time remaining.
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* Note that even after stopping a timer, one more tick may
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* still occur.
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* This method is MT-safe; i.e. it is synchronized but for
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* implementation reasons, the synchronized modifier cannot
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* be included in the method declaration.
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*/
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public void stop() {
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long now = System.currentTimeMillis();
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synchronized (timerThread) {
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synchronized (this) {
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if (!stopped) {
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TimerThread.dequeue(this);
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remainingTime = Math.max(0, sleepUntil - now);
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sleepUntil = now; // stop time
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stopped = true;
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}
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}
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}
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}
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/**
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* Continue the timer. The next tick will come at getRemainingTime()
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* milliseconds later. If the timer is not stopped, this
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* call will be a no-op.
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* This method is MT-safe; i.e. it is synchronized but for
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* implementation reasons, the synchronized modifier cannot
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* be included in the method declaration.
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*/
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public void cont() {
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synchronized (timerThread) {
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synchronized (this) {
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if (stopped) {
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// The TimerTickThread avoids requeuing the
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// timer only if the sleepUntil value has changed.
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// The following guarantees that the sleepUntil
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// value will be different; without this guarantee,
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// it's theoretically possible for the timer to be
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// inserted twice.
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sleepUntil = Math.max(sleepUntil + 1,
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System.currentTimeMillis() + remainingTime);
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TimerThread.enqueue(this);
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stopped = false;
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}
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}
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}
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}
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/**
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* Resets the timer's remaining time to the timer's interval.
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* If the timer's running state is not altered.
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*/
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public void reset() {
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synchronized (timerThread) {
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synchronized (this) {
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setRemainingTime(interval);
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}
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}
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}
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/**
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* Returns the time at which the timer was last stopped. The
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* return value is valid only if the timer is stopped.
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*/
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public synchronized long getStopTime() {
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return sleepUntil;
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}
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/**
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* Returns the timer's interval.
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*/
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public synchronized long getInterval() {
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return interval;
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}
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/**
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* Changes the timer's interval. The new interval setting
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* does not take effect until after the next tick.
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* This method does not alter the remaining time or the
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* running state of the timer.
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* @param interval new interval of the timer in milliseconds
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*/
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public synchronized void setInterval(long interval) {
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this.interval = interval;
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}
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/**
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* Returns the remaining time before the timer's next tick.
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* The return value is valid only if timer is stopped.
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*/
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public synchronized long getRemainingTime() {
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return remainingTime;
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}
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/**
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* Sets the remaining time before the timer's next tick.
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* This method does not alter the timer's running state.
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* This method is MT-safe; i.e. it is synchronized but for
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* implementation reasons, the synchronized modifier cannot
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* be included in the method declaration.
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* @param time new remaining time in milliseconds.
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*/
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public void setRemainingTime(long time) {
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synchronized (timerThread) {
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synchronized (this) {
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if (stopped) {
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remainingTime = time;
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} else {
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stop();
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remainingTime = time;
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cont();
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}
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}
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}
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}
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/**
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* In regular mode, a timer ticks at the specified interval,
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* regardless of how long the owner's tick() method takes.
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* While the timer is running, no ticks are ever discarded.
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* That means that if the owner's tick() method takes longer
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* than the interval, the ticks that would have occurred are
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* delivered immediately.
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*
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* In irregular mode, a timer starts delaying for exactly
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* the specified interval only after the tick() method returns.
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*/
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public synchronized void setRegular(boolean regular) {
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this.regular = regular;
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}
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/*
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* This method is used only for testing purposes.
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*/
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protected Thread getTimerThread() {
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return TimerThread.timerThread;
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}
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}
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/*
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325 |
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326 |
This class implements the timer queue and is exclusively used by the
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Timer class. There are only two methods exported to the Timer class -
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enqueue, for inserting a timer into queue and dequeue, for removing
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a timer from the queue.
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A timer in the timer queue is awaiting a tick. When a timer is to be
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ticked, it is removed from the timer queue before the owner's tick()
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method is called.
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A single timer thread manages the timer queue. This timer thread
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looks at the head of the timer queue and delays until it's time for
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the timer to tick. When the time comes, the timer thread creates a
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callback thread to call the timer owner's tick() method. The timer
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thread then processes the next timer in the queue.
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When a timer is inserted at the head of the queue, the timer thread is
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notified. This causes the timer thread to prematurely wake up and
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process the new head of the queue.
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*/
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class TimerThread extends Thread {
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/*
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* Set to true to get debugging output.
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*/
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public static boolean debug = false;
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|
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353 |
/*
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* This is a handle to the thread managing the thread queue.
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355 |
*/
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static TimerThread timerThread;
|
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357 |
|
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358 |
/*
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|
359 |
* This flag is set if the timer thread has been notified
|
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360 |
* while it was in the timed wait. This flag allows the
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361 |
* timer thread to tell whether or not the wait completed.
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362 |
*/
|
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363 |
static boolean notified = false;
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364 |
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365 |
protected TimerThread() {
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366 |
super("TimerThread");
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|
367 |
timerThread = this;
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368 |
start();
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369 |
}
|
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370 |
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|
371 |
public synchronized void run() {
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372 |
while (true) {
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373 |
long delay;
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374 |
|
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375 |
while (timerQueue == null) {
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376 |
try {
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377 |
wait();
|
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378 |
} catch (InterruptedException ex) {
|
|
379 |
// Just drop through and check timerQueue.
|
|
380 |
}
|
|
381 |
}
|
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382 |
notified = false;
|
|
383 |
delay = timerQueue.sleepUntil - System.currentTimeMillis();
|
|
384 |
if (delay > 0) {
|
|
385 |
try {
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|
386 |
wait(delay);
|
|
387 |
} catch (InterruptedException ex) {
|
|
388 |
// Just drop through.
|
|
389 |
}
|
|
390 |
}
|
|
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// remove from timer queue.
|
|
392 |
if (!notified) {
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393 |
Timer timer = timerQueue;
|
|
394 |
timerQueue = timerQueue.next;
|
|
395 |
TimerTickThread thr = TimerTickThread.call(
|
|
396 |
timer, timer.sleepUntil);
|
|
397 |
if (debug) {
|
|
398 |
long delta = (System.currentTimeMillis() - timer.sleepUntil);
|
|
399 |
System.out.println("tick(" + thr.getName() + ","
|
|
400 |
+ timer.interval + ","+delta+ ")");
|
|
401 |
if (delta > 250) {
|
|
402 |
System.out.println("*** BIG DELAY ***");
|
|
403 |
}
|
|
404 |
}
|
|
405 |
}
|
|
406 |
}
|
|
407 |
}
|
|
408 |
|
|
409 |
/* *******************************************************
|
|
410 |
Timer Queue
|
|
411 |
******************************************************* */
|
|
412 |
|
|
413 |
/*
|
|
414 |
* The timer queue is a queue of timers waiting to tick.
|
|
415 |
*/
|
|
416 |
static Timer timerQueue = null;
|
|
417 |
|
|
418 |
/*
|
|
419 |
* Uses timer.sleepUntil to determine where in the queue
|
|
420 |
* to insert the timer object.
|
|
421 |
* A new ticker thread is created only if the timer
|
|
422 |
* is inserted at the beginning of the queue.
|
|
423 |
* The timer must not already be in the queue.
|
|
424 |
* Assumes the caller has the TimerThread monitor.
|
|
425 |
*/
|
|
426 |
static protected void enqueue(Timer timer) {
|
|
427 |
Timer prev = null;
|
|
428 |
Timer cur = timerQueue;
|
|
429 |
|
|
430 |
if (cur == null || timer.sleepUntil <= cur.sleepUntil) {
|
|
431 |
// insert at front of queue
|
|
432 |
timer.next = timerQueue;
|
|
433 |
timerQueue = timer;
|
|
434 |
notified = true;
|
|
435 |
timerThread.notify();
|
|
436 |
} else {
|
|
437 |
do {
|
|
438 |
prev = cur;
|
|
439 |
cur = cur.next;
|
|
440 |
} while (cur != null && timer.sleepUntil > cur.sleepUntil);
|
|
441 |
// insert or append to the timer queue
|
|
442 |
timer.next = cur;
|
|
443 |
prev.next = timer;
|
|
444 |
}
|
|
445 |
if (debug) {
|
|
446 |
long now = System.currentTimeMillis();
|
|
447 |
|
|
448 |
System.out.print(Thread.currentThread().getName()
|
|
449 |
+ ": enqueue " + timer.interval + ": ");
|
|
450 |
cur = timerQueue;
|
|
451 |
while(cur != null) {
|
|
452 |
long delta = cur.sleepUntil - now;
|
|
453 |
System.out.print(cur.interval + "(" + delta + ") ");
|
|
454 |
cur = cur.next;
|
|
455 |
}
|
|
456 |
System.out.println();
|
|
457 |
}
|
|
458 |
}
|
|
459 |
|
|
460 |
/*
|
|
461 |
* If the timer is not in the queue, returns false;
|
|
462 |
* otherwise removes the timer from the timer queue and returns true.
|
|
463 |
* Assumes the caller has the TimerThread monitor.
|
|
464 |
*/
|
|
465 |
static protected boolean dequeue(Timer timer) {
|
|
466 |
Timer prev = null;
|
|
467 |
Timer cur = timerQueue;
|
|
468 |
|
|
469 |
while (cur != null && cur != timer) {
|
|
470 |
prev = cur;
|
|
471 |
cur = cur.next;
|
|
472 |
}
|
|
473 |
if (cur == null) {
|
|
474 |
if (debug) {
|
|
475 |
System.out.println(Thread.currentThread().getName()
|
|
476 |
+ ": dequeue " + timer.interval + ": no-op");
|
|
477 |
}
|
|
478 |
return false;
|
|
479 |
} if (prev == null) {
|
|
480 |
timerQueue = timer.next;
|
|
481 |
notified = true;
|
|
482 |
timerThread.notify();
|
|
483 |
} else {
|
|
484 |
prev.next = timer.next;
|
|
485 |
}
|
|
486 |
timer.next = null;
|
|
487 |
if (debug) {
|
|
488 |
long now = System.currentTimeMillis();
|
|
489 |
|
|
490 |
System.out.print(Thread.currentThread().getName()
|
|
491 |
+ ": dequeue " + timer.interval + ": ");
|
|
492 |
cur = timerQueue;
|
|
493 |
while(cur != null) {
|
|
494 |
long delta = cur.sleepUntil - now;
|
|
495 |
System.out.print(cur.interval + "(" + delta + ") ");
|
|
496 |
cur = cur.next;
|
|
497 |
}
|
|
498 |
System.out.println();
|
|
499 |
}
|
|
500 |
return true;
|
|
501 |
}
|
|
502 |
|
|
503 |
/*
|
|
504 |
* Inserts the timer back into the queue. This method
|
|
505 |
* is used by a callback thread after it has called the
|
|
506 |
* timer owner's tick() method. This method recomputes
|
|
507 |
* the sleepUntil field.
|
|
508 |
* Assumes the caller has the TimerThread and Timer monitor.
|
|
509 |
*/
|
|
510 |
protected static void requeue(Timer timer) {
|
|
511 |
if (!timer.stopped) {
|
|
512 |
long now = System.currentTimeMillis();
|
|
513 |
if (timer.regular) {
|
|
514 |
timer.sleepUntil += timer.interval;
|
|
515 |
} else {
|
|
516 |
timer.sleepUntil = now + timer.interval;
|
|
517 |
}
|
|
518 |
enqueue(timer);
|
|
519 |
} else if (debug) {
|
|
520 |
System.out.println(Thread.currentThread().getName()
|
|
521 |
+ ": requeue " + timer.interval + ": no-op");
|
|
522 |
}
|
|
523 |
}
|
|
524 |
}
|
|
525 |
|
|
526 |
/*
|
|
527 |
|
|
528 |
This class implements a simple thread whose only purpose is to call a
|
|
529 |
timer owner's tick() method. A small fixed-sized pool of threads is
|
|
530 |
maintained and is protected by the class monitor. If the pool is
|
|
531 |
exhausted, a new thread is temporarily created and destroyed when
|
|
532 |
done.
|
|
533 |
|
|
534 |
A thread that's in the pool waits on it's own monitor. When the
|
|
535 |
thread is retrieved from the pool, the retriever notifies the thread's
|
|
536 |
monitor.
|
|
537 |
|
|
538 |
*/
|
|
539 |
|
|
540 |
class TimerTickThread extends Thread {
|
|
541 |
/*
|
|
542 |
* Maximum size of the thread pool.
|
|
543 |
*/
|
|
544 |
static final int MAX_POOL_SIZE = 3;
|
|
545 |
|
|
546 |
/*
|
|
547 |
* Number of threads in the pool.
|
|
548 |
*/
|
|
549 |
static int curPoolSize = 0;
|
|
550 |
|
|
551 |
/*
|
|
552 |
* The pool of timer threads.
|
|
553 |
*/
|
|
554 |
static TimerTickThread pool = null;
|
|
555 |
|
|
556 |
/*
|
|
557 |
* Is used when linked into the thread pool.
|
|
558 |
*/
|
|
559 |
TimerTickThread next = null;
|
|
560 |
|
|
561 |
/*
|
|
562 |
* This is the handle to the timer whose owner's
|
|
563 |
* tick() method will be called.
|
|
564 |
*/
|
|
565 |
Timer timer;
|
|
566 |
|
|
567 |
/*
|
|
568 |
* The value of a timer's sleepUntil value is captured here.
|
|
569 |
* This is used to determine whether or not the timer should
|
|
570 |
* be reinserted into the queue. If the timer's sleepUntil
|
|
571 |
* value has changed, the timer is not reinserted.
|
|
572 |
*/
|
|
573 |
long lastSleepUntil;
|
|
574 |
|
|
575 |
/*
|
|
576 |
* Creates a new callback thread to call the timer owner's
|
|
577 |
* tick() method. A thread is taken from the pool if one
|
|
578 |
* is available, otherwise, a new thread is created.
|
|
579 |
* The thread handle is returned.
|
|
580 |
*/
|
|
581 |
protected static synchronized TimerTickThread call(
|
|
582 |
Timer timer, long sleepUntil) {
|
|
583 |
TimerTickThread thread = pool;
|
|
584 |
|
|
585 |
if (thread == null) {
|
|
586 |
// create one.
|
|
587 |
thread = new TimerTickThread();
|
|
588 |
thread.timer = timer;
|
|
589 |
thread.lastSleepUntil = sleepUntil;
|
|
590 |
thread.start();
|
|
591 |
} else {
|
|
592 |
pool = pool.next;
|
|
593 |
thread.timer = timer;
|
|
594 |
thread.lastSleepUntil = sleepUntil;
|
|
595 |
synchronized (thread) {
|
|
596 |
thread.notify();
|
|
597 |
}
|
|
598 |
}
|
|
599 |
return thread;
|
|
600 |
}
|
|
601 |
|
|
602 |
/*
|
|
603 |
* Returns false if the thread should simply exit;
|
|
604 |
* otherwise the thread is returned the pool, where
|
|
605 |
* it waits to be notified. (I did try to use the
|
|
606 |
* class monitor but the time between the notify
|
|
607 |
* and breaking out of the wait seemed to take
|
|
608 |
* significantly longer; need to look into this later.)
|
|
609 |
*/
|
|
610 |
private boolean returnToPool() {
|
|
611 |
synchronized (getClass()) {
|
|
612 |
if (curPoolSize >= MAX_POOL_SIZE) {
|
|
613 |
return false;
|
|
614 |
}
|
|
615 |
next = pool;
|
|
616 |
pool = this;
|
|
617 |
curPoolSize++;
|
|
618 |
timer = null;
|
|
619 |
}
|
|
620 |
while (timer == null) {
|
|
621 |
synchronized (this) {
|
|
622 |
try {
|
|
623 |
wait();
|
|
624 |
} catch (InterruptedException ex) {
|
|
625 |
// Just drop through and retest timer.
|
|
626 |
}
|
|
627 |
}
|
|
628 |
}
|
|
629 |
synchronized (getClass()) {
|
|
630 |
curPoolSize--;
|
|
631 |
}
|
|
632 |
return true;
|
|
633 |
}
|
|
634 |
|
|
635 |
public void run() {
|
|
636 |
do {
|
|
637 |
timer.owner.tick(timer);
|
|
638 |
synchronized (TimerThread.timerThread) {
|
|
639 |
synchronized (timer) {
|
|
640 |
if (lastSleepUntil == timer.sleepUntil) {
|
|
641 |
TimerThread.requeue(timer);
|
|
642 |
}
|
|
643 |
}
|
|
644 |
}
|
|
645 |
} while (returnToPool());
|
|
646 |
}
|
|
647 |
}
|