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/*
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* Copyright (c) 1999, 2008, 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 java.util;
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import java.util.Date;
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import java.util.concurrent.atomic.AtomicInteger;
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import org.apidesign.bck2brwsr.core.JavaScriptBody;
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/**
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* A facility for threads to schedule tasks for future execution in a
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* background thread. Tasks may be scheduled for one-time execution, or for
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* repeated execution at regular intervals.
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*
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* <p>Corresponding to each <tt>Timer</tt> object is a single background
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* thread that is used to execute all of the timer's tasks, sequentially.
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* Timer tasks should complete quickly. If a timer task takes excessive time
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* to complete, it "hogs" the timer's task execution thread. This can, in
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* turn, delay the execution of subsequent tasks, which may "bunch up" and
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* execute in rapid succession when (and if) the offending task finally
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* completes.
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*
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* <p>After the last live reference to a <tt>Timer</tt> object goes away
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* <i>and</i> all outstanding tasks have completed execution, the timer's task
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* execution thread terminates gracefully (and becomes subject to garbage
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* collection). However, this can take arbitrarily long to occur. By
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* default, the task execution thread does not run as a <i>daemon thread</i>,
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* so it is capable of keeping an application from terminating. If a caller
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* wants to terminate a timer's task execution thread rapidly, the caller
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* should invoke the timer's <tt>cancel</tt> method.
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*
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* <p>If the timer's task execution thread terminates unexpectedly, for
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* example, because its <tt>stop</tt> method is invoked, any further
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* attempt to schedule a task on the timer will result in an
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* <tt>IllegalStateException</tt>, as if the timer's <tt>cancel</tt>
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* method had been invoked.
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*
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* <p>This class is thread-safe: multiple threads can share a single
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* <tt>Timer</tt> object without the need for external synchronization.
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*
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* <p>This class does <i>not</i> offer real-time guarantees: it schedules
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* tasks using the <tt>Object.wait(long)</tt> method.
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*
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* <p>Java 5.0 introduced the {@code java.util.concurrent} package and
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* one of the concurrency utilities therein is the {@link
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* java.util.concurrent.ScheduledThreadPoolExecutor
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* ScheduledThreadPoolExecutor} which is a thread pool for repeatedly
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* executing tasks at a given rate or delay. It is effectively a more
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* versatile replacement for the {@code Timer}/{@code TimerTask}
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* combination, as it allows multiple service threads, accepts various
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* time units, and doesn't require subclassing {@code TimerTask} (just
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* implement {@code Runnable}). Configuring {@code
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* ScheduledThreadPoolExecutor} with one thread makes it equivalent to
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* {@code Timer}.
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*
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* <p>Implementation note: This class scales to large numbers of concurrently
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* scheduled tasks (thousands should present no problem). Internally,
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* it uses a binary heap to represent its task queue, so the cost to schedule
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* a task is O(log n), where n is the number of concurrently scheduled tasks.
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*
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* <p>Implementation note: All constructors start a timer thread.
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*
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* @author Josh Bloch
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* @see TimerTask
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* @see Object#wait(long)
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* @since 1.3
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*/
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public class Timer {
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/**
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* The timer task queue. This data structure is shared with the timer
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* thread. The timer produces tasks, via its various schedule calls,
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* and the timer thread consumes, executing timer tasks as appropriate,
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* and removing them from the queue when they're obsolete.
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*/
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private final TaskQueue queue = new TaskQueue();
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/**
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* The timer thread.
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*/
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private final TimerThread thread = new TimerThread(queue);
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/**
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* This object causes the timer's task execution thread to exit
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* gracefully when there are no live references to the Timer object and no
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* tasks in the timer queue. It is used in preference to a finalizer on
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* Timer as such a finalizer would be susceptible to a subclass's
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* finalizer forgetting to call it.
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*/
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private final Object threadReaper = new Object() {
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protected void finalize() throws Throwable {
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synchronized(queue) {
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thread.newTasksMayBeScheduled = false;
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thread.notifyQueue(1); // In case queue is empty.
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}
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}
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};
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/**
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* This ID is used to generate thread names.
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*/
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private final static AtomicInteger nextSerialNumber = new AtomicInteger(0);
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private static int serialNumber() {
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return nextSerialNumber.getAndIncrement();
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}
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/**
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* Creates a new timer. The associated thread does <i>not</i>
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* {@linkplain Thread#setDaemon run as a daemon}.
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*/
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public Timer() {
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this("Timer-" + serialNumber());
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}
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/**
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* Creates a new timer whose associated thread may be specified to
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* {@linkplain Thread#setDaemon run as a daemon}.
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* A daemon thread is called for if the timer will be used to
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* schedule repeating "maintenance activities", which must be
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* performed as long as the application is running, but should not
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* prolong the lifetime of the application.
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*
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* @param isDaemon true if the associated thread should run as a daemon.
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*/
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public Timer(boolean isDaemon) {
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this("Timer-" + serialNumber(), isDaemon);
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}
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/**
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* Creates a new timer whose associated thread has the specified name.
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* The associated thread does <i>not</i>
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* {@linkplain Thread#setDaemon run as a daemon}.
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*
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* @param name the name of the associated thread
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* @throws NullPointerException if {@code name} is null
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* @since 1.5
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*/
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public Timer(String name) {
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}
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/**
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* Creates a new timer whose associated thread has the specified name,
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* and may be specified to
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* {@linkplain Thread#setDaemon run as a daemon}.
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*
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* @param name the name of the associated thread
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* @param isDaemon true if the associated thread should run as a daemon
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* @throws NullPointerException if {@code name} is null
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* @since 1.5
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*/
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public Timer(String name, boolean isDaemon) {
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}
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/**
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* Schedules the specified task for execution after the specified delay.
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*
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* @param task task to be scheduled.
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* @param delay delay in milliseconds before task is to be executed.
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* @throws IllegalArgumentException if <tt>delay</tt> is negative, or
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* <tt>delay + System.currentTimeMillis()</tt> is negative.
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* @throws IllegalStateException if task was already scheduled or
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* cancelled, timer was cancelled, or timer thread terminated.
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* @throws NullPointerException if {@code task} is null
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*/
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public void schedule(TimerTask task, long delay) {
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if (delay < 0)
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throw new IllegalArgumentException("Negative delay.");
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sched(task, System.currentTimeMillis()+delay, 0);
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}
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/**
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* Schedules the specified task for execution at the specified time. If
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* the time is in the past, the task is scheduled for immediate execution.
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*
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* @param task task to be scheduled.
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* @param time time at which task is to be executed.
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* @throws IllegalArgumentException if <tt>time.getTime()</tt> is negative.
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* @throws IllegalStateException if task was already scheduled or
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* cancelled, timer was cancelled, or timer thread terminated.
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* @throws NullPointerException if {@code task} or {@code time} is null
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*/
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public void schedule(TimerTask task, Date time) {
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sched(task, time.getTime(), 0);
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}
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/**
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* Schedules the specified task for repeated <i>fixed-delay execution</i>,
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* beginning after the specified delay. Subsequent executions take place
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* at approximately regular intervals separated by the specified period.
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*
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* <p>In fixed-delay execution, each execution is scheduled relative to
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* the actual execution time of the previous execution. If an execution
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* is delayed for any reason (such as garbage collection or other
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* background activity), subsequent executions will be delayed as well.
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* In the long run, the frequency of execution will generally be slightly
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* lower than the reciprocal of the specified period (assuming the system
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* clock underlying <tt>Object.wait(long)</tt> is accurate).
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*
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* <p>Fixed-delay execution is appropriate for recurring activities
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* that require "smoothness." In other words, it is appropriate for
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* activities where it is more important to keep the frequency accurate
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* in the short run than in the long run. This includes most animation
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* tasks, such as blinking a cursor at regular intervals. It also includes
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* tasks wherein regular activity is performed in response to human
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* input, such as automatically repeating a character as long as a key
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* is held down.
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*
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* @param task task to be scheduled.
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* @param delay delay in milliseconds before task is to be executed.
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* @param period time in milliseconds between successive task executions.
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* @throws IllegalArgumentException if {@code delay < 0}, or
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* {@code delay + System.currentTimeMillis() < 0}, or
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* {@code period <= 0}
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* @throws IllegalStateException if task was already scheduled or
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* cancelled, timer was cancelled, or timer thread terminated.
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* @throws NullPointerException if {@code task} is null
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*/
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public void schedule(TimerTask task, long delay, long period) {
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if (delay < 0)
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throw new IllegalArgumentException("Negative delay.");
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if (period <= 0)
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throw new IllegalArgumentException("Non-positive period.");
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sched(task, System.currentTimeMillis()+delay, -period);
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}
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/**
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* Schedules the specified task for repeated <i>fixed-delay execution</i>,
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* beginning at the specified time. Subsequent executions take place at
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* approximately regular intervals, separated by the specified period.
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*
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* <p>In fixed-delay execution, each execution is scheduled relative to
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* the actual execution time of the previous execution. If an execution
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* is delayed for any reason (such as garbage collection or other
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* background activity), subsequent executions will be delayed as well.
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* In the long run, the frequency of execution will generally be slightly
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* lower than the reciprocal of the specified period (assuming the system
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* clock underlying <tt>Object.wait(long)</tt> is accurate). As a
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* consequence of the above, if the scheduled first time is in the past,
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* it is scheduled for immediate execution.
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*
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* <p>Fixed-delay execution is appropriate for recurring activities
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* that require "smoothness." In other words, it is appropriate for
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* activities where it is more important to keep the frequency accurate
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* in the short run than in the long run. This includes most animation
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* tasks, such as blinking a cursor at regular intervals. It also includes
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* tasks wherein regular activity is performed in response to human
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* input, such as automatically repeating a character as long as a key
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* is held down.
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*
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* @param task task to be scheduled.
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* @param firstTime First time at which task is to be executed.
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* @param period time in milliseconds between successive task executions.
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* @throws IllegalArgumentException if {@code firstTime.getTime() < 0}, or
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* {@code period <= 0}
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* @throws IllegalStateException if task was already scheduled or
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* cancelled, timer was cancelled, or timer thread terminated.
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|
278 |
* @throws NullPointerException if {@code task} or {@code firstTime} is null
|
jtulach@1405
|
279 |
*/
|
jtulach@1405
|
280 |
public void schedule(TimerTask task, Date firstTime, long period) {
|
jtulach@1405
|
281 |
if (period <= 0)
|
jtulach@1405
|
282 |
throw new IllegalArgumentException("Non-positive period.");
|
jtulach@1405
|
283 |
sched(task, firstTime.getTime(), -period);
|
jtulach@1405
|
284 |
}
|
jtulach@1405
|
285 |
|
jtulach@1405
|
286 |
/**
|
jtulach@1405
|
287 |
* Schedules the specified task for repeated <i>fixed-rate execution</i>,
|
jtulach@1405
|
288 |
* beginning after the specified delay. Subsequent executions take place
|
jtulach@1405
|
289 |
* at approximately regular intervals, separated by the specified period.
|
jtulach@1405
|
290 |
*
|
jtulach@1405
|
291 |
* <p>In fixed-rate execution, each execution is scheduled relative to the
|
jtulach@1405
|
292 |
* scheduled execution time of the initial execution. If an execution is
|
jtulach@1405
|
293 |
* delayed for any reason (such as garbage collection or other background
|
jtulach@1405
|
294 |
* activity), two or more executions will occur in rapid succession to
|
jtulach@1405
|
295 |
* "catch up." In the long run, the frequency of execution will be
|
jtulach@1405
|
296 |
* exactly the reciprocal of the specified period (assuming the system
|
jtulach@1405
|
297 |
* clock underlying <tt>Object.wait(long)</tt> is accurate).
|
jtulach@1405
|
298 |
*
|
jtulach@1405
|
299 |
* <p>Fixed-rate execution is appropriate for recurring activities that
|
jtulach@1405
|
300 |
* are sensitive to <i>absolute</i> time, such as ringing a chime every
|
jtulach@1405
|
301 |
* hour on the hour, or running scheduled maintenance every day at a
|
jtulach@1405
|
302 |
* particular time. It is also appropriate for recurring activities
|
jtulach@1405
|
303 |
* where the total time to perform a fixed number of executions is
|
jtulach@1405
|
304 |
* important, such as a countdown timer that ticks once every second for
|
jtulach@1405
|
305 |
* ten seconds. Finally, fixed-rate execution is appropriate for
|
jtulach@1405
|
306 |
* scheduling multiple repeating timer tasks that must remain synchronized
|
jtulach@1405
|
307 |
* with respect to one another.
|
jtulach@1405
|
308 |
*
|
jtulach@1405
|
309 |
* @param task task to be scheduled.
|
jtulach@1405
|
310 |
* @param delay delay in milliseconds before task is to be executed.
|
jtulach@1405
|
311 |
* @param period time in milliseconds between successive task executions.
|
jtulach@1405
|
312 |
* @throws IllegalArgumentException if {@code delay < 0}, or
|
jtulach@1405
|
313 |
* {@code delay + System.currentTimeMillis() < 0}, or
|
jtulach@1405
|
314 |
* {@code period <= 0}
|
jtulach@1405
|
315 |
* @throws IllegalStateException if task was already scheduled or
|
jtulach@1405
|
316 |
* cancelled, timer was cancelled, or timer thread terminated.
|
jtulach@1405
|
317 |
* @throws NullPointerException if {@code task} is null
|
jtulach@1405
|
318 |
*/
|
jtulach@1405
|
319 |
public void scheduleAtFixedRate(TimerTask task, long delay, long period) {
|
jtulach@1405
|
320 |
if (delay < 0)
|
jtulach@1405
|
321 |
throw new IllegalArgumentException("Negative delay.");
|
jtulach@1405
|
322 |
if (period <= 0)
|
jtulach@1405
|
323 |
throw new IllegalArgumentException("Non-positive period.");
|
jtulach@1405
|
324 |
sched(task, System.currentTimeMillis()+delay, period);
|
jtulach@1405
|
325 |
}
|
jtulach@1405
|
326 |
|
jtulach@1405
|
327 |
/**
|
jtulach@1405
|
328 |
* Schedules the specified task for repeated <i>fixed-rate execution</i>,
|
jtulach@1405
|
329 |
* beginning at the specified time. Subsequent executions take place at
|
jtulach@1405
|
330 |
* approximately regular intervals, separated by the specified period.
|
jtulach@1405
|
331 |
*
|
jtulach@1405
|
332 |
* <p>In fixed-rate execution, each execution is scheduled relative to the
|
jtulach@1405
|
333 |
* scheduled execution time of the initial execution. If an execution is
|
jtulach@1405
|
334 |
* delayed for any reason (such as garbage collection or other background
|
jtulach@1405
|
335 |
* activity), two or more executions will occur in rapid succession to
|
jtulach@1405
|
336 |
* "catch up." In the long run, the frequency of execution will be
|
jtulach@1405
|
337 |
* exactly the reciprocal of the specified period (assuming the system
|
jtulach@1405
|
338 |
* clock underlying <tt>Object.wait(long)</tt> is accurate). As a
|
jtulach@1405
|
339 |
* consequence of the above, if the scheduled first time is in the past,
|
jtulach@1405
|
340 |
* then any "missed" executions will be scheduled for immediate "catch up"
|
jtulach@1405
|
341 |
* execution.
|
jtulach@1405
|
342 |
*
|
jtulach@1405
|
343 |
* <p>Fixed-rate execution is appropriate for recurring activities that
|
jtulach@1405
|
344 |
* are sensitive to <i>absolute</i> time, such as ringing a chime every
|
jtulach@1405
|
345 |
* hour on the hour, or running scheduled maintenance every day at a
|
jtulach@1405
|
346 |
* particular time. It is also appropriate for recurring activities
|
jtulach@1405
|
347 |
* where the total time to perform a fixed number of executions is
|
jtulach@1405
|
348 |
* important, such as a countdown timer that ticks once every second for
|
jtulach@1405
|
349 |
* ten seconds. Finally, fixed-rate execution is appropriate for
|
jtulach@1405
|
350 |
* scheduling multiple repeating timer tasks that must remain synchronized
|
jtulach@1405
|
351 |
* with respect to one another.
|
jtulach@1405
|
352 |
*
|
jtulach@1405
|
353 |
* @param task task to be scheduled.
|
jtulach@1405
|
354 |
* @param firstTime First time at which task is to be executed.
|
jtulach@1405
|
355 |
* @param period time in milliseconds between successive task executions.
|
jtulach@1405
|
356 |
* @throws IllegalArgumentException if {@code firstTime.getTime() < 0} or
|
jtulach@1405
|
357 |
* {@code period <= 0}
|
jtulach@1405
|
358 |
* @throws IllegalStateException if task was already scheduled or
|
jtulach@1405
|
359 |
* cancelled, timer was cancelled, or timer thread terminated.
|
jtulach@1405
|
360 |
* @throws NullPointerException if {@code task} or {@code firstTime} is null
|
jtulach@1405
|
361 |
*/
|
jtulach@1405
|
362 |
public void scheduleAtFixedRate(TimerTask task, Date firstTime,
|
jtulach@1405
|
363 |
long period) {
|
jtulach@1405
|
364 |
if (period <= 0)
|
jtulach@1405
|
365 |
throw new IllegalArgumentException("Non-positive period.");
|
jtulach@1405
|
366 |
sched(task, firstTime.getTime(), period);
|
jtulach@1405
|
367 |
}
|
jtulach@1405
|
368 |
|
jtulach@1405
|
369 |
/**
|
jtulach@1405
|
370 |
* Schedule the specified timer task for execution at the specified
|
jtulach@1405
|
371 |
* time with the specified period, in milliseconds. If period is
|
jtulach@1405
|
372 |
* positive, the task is scheduled for repeated execution; if period is
|
jtulach@1405
|
373 |
* zero, the task is scheduled for one-time execution. Time is specified
|
jtulach@1405
|
374 |
* in Date.getTime() format. This method checks timer state, task state,
|
jtulach@1405
|
375 |
* and initial execution time, but not period.
|
jtulach@1405
|
376 |
*
|
jtulach@1405
|
377 |
* @throws IllegalArgumentException if <tt>time</tt> is negative.
|
jtulach@1405
|
378 |
* @throws IllegalStateException if task was already scheduled or
|
jtulach@1405
|
379 |
* cancelled, timer was cancelled, or timer thread terminated.
|
jtulach@1405
|
380 |
* @throws NullPointerException if {@code task} is null
|
jtulach@1405
|
381 |
*/
|
jtulach@1405
|
382 |
private void sched(TimerTask task, long time, long period) {
|
jtulach@1405
|
383 |
if (time < 0)
|
jtulach@1405
|
384 |
throw new IllegalArgumentException("Illegal execution time.");
|
jtulach@1405
|
385 |
|
jtulach@1405
|
386 |
// Constrain value of period sufficiently to prevent numeric
|
jtulach@1405
|
387 |
// overflow while still being effectively infinitely large.
|
jtulach@1405
|
388 |
if (Math.abs(period) > (Long.MAX_VALUE >> 1))
|
jtulach@1405
|
389 |
period >>= 1;
|
jtulach@1405
|
390 |
|
jtulach@1405
|
391 |
synchronized(queue) {
|
jtulach@1405
|
392 |
if (!thread.newTasksMayBeScheduled)
|
jtulach@1405
|
393 |
throw new IllegalStateException("Timer already cancelled.");
|
jtulach@1405
|
394 |
|
jtulach@1405
|
395 |
synchronized(task.lock) {
|
jtulach@1405
|
396 |
if (task.state != TimerTask.VIRGIN)
|
jtulach@1405
|
397 |
throw new IllegalStateException(
|
jtulach@1405
|
398 |
"Task already scheduled or cancelled");
|
jtulach@1405
|
399 |
task.nextExecutionTime = time;
|
jtulach@1405
|
400 |
task.period = period;
|
jtulach@1405
|
401 |
task.state = TimerTask.SCHEDULED;
|
jtulach@1405
|
402 |
}
|
jtulach@1405
|
403 |
|
jtulach@1405
|
404 |
queue.add(task);
|
jtulach@1405
|
405 |
if (queue.getMin() == task)
|
jaroslav@1407
|
406 |
thread.notifyQueue(1);
|
jtulach@1405
|
407 |
}
|
jtulach@1405
|
408 |
}
|
jtulach@1405
|
409 |
|
jtulach@1405
|
410 |
/**
|
jtulach@1405
|
411 |
* Terminates this timer, discarding any currently scheduled tasks.
|
jtulach@1405
|
412 |
* Does not interfere with a currently executing task (if it exists).
|
jtulach@1405
|
413 |
* Once a timer has been terminated, its execution thread terminates
|
jtulach@1405
|
414 |
* gracefully, and no more tasks may be scheduled on it.
|
jtulach@1405
|
415 |
*
|
jtulach@1405
|
416 |
* <p>Note that calling this method from within the run method of a
|
jtulach@1405
|
417 |
* timer task that was invoked by this timer absolutely guarantees that
|
jtulach@1405
|
418 |
* the ongoing task execution is the last task execution that will ever
|
jtulach@1405
|
419 |
* be performed by this timer.
|
jtulach@1405
|
420 |
*
|
jtulach@1405
|
421 |
* <p>This method may be called repeatedly; the second and subsequent
|
jtulach@1405
|
422 |
* calls have no effect.
|
jtulach@1405
|
423 |
*/
|
jtulach@1405
|
424 |
public void cancel() {
|
jtulach@1405
|
425 |
synchronized(queue) {
|
jtulach@1405
|
426 |
thread.newTasksMayBeScheduled = false;
|
jtulach@1405
|
427 |
queue.clear();
|
jaroslav@1407
|
428 |
thread.notifyQueue(1); // In case queue was already empty.
|
jtulach@1405
|
429 |
}
|
jtulach@1405
|
430 |
}
|
jaroslav@1407
|
431 |
|
jtulach@1405
|
432 |
/**
|
jtulach@1405
|
433 |
* Removes all cancelled tasks from this timer's task queue. <i>Calling
|
jtulach@1405
|
434 |
* this method has no effect on the behavior of the timer</i>, but
|
jtulach@1405
|
435 |
* eliminates the references to the cancelled tasks from the queue.
|
jtulach@1405
|
436 |
* If there are no external references to these tasks, they become
|
jtulach@1405
|
437 |
* eligible for garbage collection.
|
jtulach@1405
|
438 |
*
|
jtulach@1405
|
439 |
* <p>Most programs will have no need to call this method.
|
jtulach@1405
|
440 |
* It is designed for use by the rare application that cancels a large
|
jtulach@1405
|
441 |
* number of tasks. Calling this method trades time for space: the
|
jtulach@1405
|
442 |
* runtime of the method may be proportional to n + c log n, where n
|
jtulach@1405
|
443 |
* is the number of tasks in the queue and c is the number of cancelled
|
jtulach@1405
|
444 |
* tasks.
|
jtulach@1405
|
445 |
*
|
jtulach@1405
|
446 |
* <p>Note that it is permissible to call this method from within a
|
jtulach@1405
|
447 |
* a task scheduled on this timer.
|
jtulach@1405
|
448 |
*
|
jtulach@1405
|
449 |
* @return the number of tasks removed from the queue.
|
jtulach@1405
|
450 |
* @since 1.5
|
jtulach@1405
|
451 |
*/
|
jtulach@1405
|
452 |
public int purge() {
|
jtulach@1405
|
453 |
int result = 0;
|
jtulach@1405
|
454 |
|
jtulach@1405
|
455 |
synchronized(queue) {
|
jtulach@1405
|
456 |
for (int i = queue.size(); i > 0; i--) {
|
jtulach@1405
|
457 |
if (queue.get(i).state == TimerTask.CANCELLED) {
|
jtulach@1405
|
458 |
queue.quickRemove(i);
|
jtulach@1405
|
459 |
result++;
|
jtulach@1405
|
460 |
}
|
jtulach@1405
|
461 |
}
|
jtulach@1405
|
462 |
|
jtulach@1405
|
463 |
if (result != 0)
|
jtulach@1405
|
464 |
queue.heapify();
|
jtulach@1405
|
465 |
}
|
jtulach@1405
|
466 |
|
jtulach@1405
|
467 |
return result;
|
jtulach@1405
|
468 |
}
|
jtulach@1405
|
469 |
}
|
jtulach@1405
|
470 |
|
jtulach@1405
|
471 |
/**
|
jtulach@1405
|
472 |
* This "helper class" implements the timer's task execution thread, which
|
jtulach@1405
|
473 |
* waits for tasks on the timer queue, executions them when they fire,
|
jtulach@1405
|
474 |
* reschedules repeating tasks, and removes cancelled tasks and spent
|
jtulach@1405
|
475 |
* non-repeating tasks from the queue.
|
jtulach@1405
|
476 |
*/
|
jaroslav@1407
|
477 |
class TimerThread implements Runnable {
|
jtulach@1405
|
478 |
/**
|
jtulach@1405
|
479 |
* This flag is set to false by the reaper to inform us that there
|
jtulach@1405
|
480 |
* are no more live references to our Timer object. Once this flag
|
jtulach@1405
|
481 |
* is true and there are no more tasks in our queue, there is no
|
jtulach@1405
|
482 |
* work left for us to do, so we terminate gracefully. Note that
|
jtulach@1405
|
483 |
* this field is protected by queue's monitor!
|
jtulach@1405
|
484 |
*/
|
jtulach@1405
|
485 |
boolean newTasksMayBeScheduled = true;
|
jtulach@1405
|
486 |
|
jtulach@1405
|
487 |
/**
|
jtulach@1405
|
488 |
* Our Timer's queue. We store this reference in preference to
|
jtulach@1405
|
489 |
* a reference to the Timer so the reference graph remains acyclic.
|
jtulach@1405
|
490 |
* Otherwise, the Timer would never be garbage-collected and this
|
jtulach@1405
|
491 |
* thread would never go away.
|
jtulach@1405
|
492 |
*/
|
jaroslav@1945
|
493 |
private final TaskQueue queue;
|
jaroslav@1945
|
494 |
private Object prevTimeout;
|
jtulach@1405
|
495 |
|
jtulach@1405
|
496 |
TimerThread(TaskQueue queue) {
|
jtulach@1405
|
497 |
this.queue = queue;
|
jtulach@1405
|
498 |
}
|
jtulach@1405
|
499 |
|
jaroslav@1407
|
500 |
void notifyQueue(int delay) {
|
jaroslav@1407
|
501 |
if (delay < 1) {
|
jaroslav@1407
|
502 |
delay = 1;
|
jaroslav@1407
|
503 |
}
|
jaroslav@1945
|
504 |
prevTimeout = setTimeout(delay, this, prevTimeout);
|
jaroslav@1407
|
505 |
}
|
jaroslav@1407
|
506 |
|
jaroslav@1945
|
507 |
@JavaScriptBody(args = { "delay", "r", "prev" }, body = ""
|
jaroslav@1945
|
508 |
// + "console.log('clear prev ' + prev);\n"
|
jaroslav@1945
|
509 |
+ "if (prev) {\n"
|
jaroslav@1945
|
510 |
+ " window.clearTimeout(prev);\n"
|
jaroslav@1945
|
511 |
+ "}\n"
|
jaroslav@1945
|
512 |
// + "console.log('schedule in ' + delay);\n"
|
jaroslav@1945
|
513 |
+ "return window.setTimeout(function() {\n"
|
jaroslav@1945
|
514 |
// + " console.log('running time');\n"
|
jaroslav@1945
|
515 |
+ " r.run__V();\n"
|
jaroslav@1945
|
516 |
// + " console.log('done running time');\n"
|
jaroslav@1945
|
517 |
+ "}, delay);\n"
|
jaroslav@1945
|
518 |
)
|
jaroslav@1945
|
519 |
private static native Object setTimeout(int delay, Runnable r, Object prev);
|
jaroslav@1945
|
520 |
|
jaroslav@1945
|
521 |
// @JavaScriptBody(args = { "msg" }, body = "console.log(msg);")
|
jaroslav@1945
|
522 |
private static void log(String msg) {
|
jaroslav@1945
|
523 |
}
|
jaroslav@1407
|
524 |
|
jaroslav@1945
|
525 |
@Override
|
jtulach@1405
|
526 |
public void run() {
|
jaroslav@1945
|
527 |
try {
|
jaroslav@1945
|
528 |
mainLoop(1);
|
jaroslav@1945
|
529 |
} finally {
|
jaroslav@1945
|
530 |
synchronized (queue) {
|
jaroslav@1945
|
531 |
if (!queue.isEmpty()) {
|
jaroslav@1945
|
532 |
long next = queue.getMin().nextExecutionTime;
|
jaroslav@1945
|
533 |
long now = System.currentTimeMillis();
|
jaroslav@1945
|
534 |
int delta = (int) (next - now);
|
jaroslav@1945
|
535 |
notifyQueue(delta);
|
jaroslav@1945
|
536 |
}
|
jaroslav@1945
|
537 |
}
|
jaroslav@1945
|
538 |
}
|
jaroslav@1407
|
539 |
// try {
|
jaroslav@1407
|
540 |
// mainLoop(0);
|
jaroslav@1407
|
541 |
// } finally {
|
jaroslav@1407
|
542 |
// // Someone killed this Thread, behave as if Timer cancelled
|
jaroslav@1407
|
543 |
// synchronized(queue) {
|
jaroslav@1407
|
544 |
// newTasksMayBeScheduled = false;
|
jaroslav@1407
|
545 |
// queue.clear(); // Eliminate obsolete references
|
jaroslav@1407
|
546 |
// }
|
jaroslav@1407
|
547 |
// }
|
jtulach@1405
|
548 |
}
|
jtulach@1405
|
549 |
|
jtulach@1405
|
550 |
/**
|
jtulach@1405
|
551 |
* The main timer loop. (See class comment.)
|
jtulach@1405
|
552 |
*/
|
jaroslav@1407
|
553 |
private void mainLoop(int inc) {
|
jaroslav@1407
|
554 |
for (int i = 0; i < 1; i += inc) {
|
jtulach@1405
|
555 |
try {
|
jtulach@1405
|
556 |
TimerTask task;
|
jtulach@1405
|
557 |
boolean taskFired;
|
jtulach@1405
|
558 |
synchronized(queue) {
|
jtulach@1405
|
559 |
// Wait for queue to become non-empty
|
jtulach@1405
|
560 |
while (queue.isEmpty() && newTasksMayBeScheduled)
|
jaroslav@1407
|
561 |
break;
|
jtulach@1405
|
562 |
if (queue.isEmpty())
|
jtulach@1405
|
563 |
break; // Queue is empty and will forever remain; die
|
jtulach@1405
|
564 |
|
jtulach@1405
|
565 |
// Queue nonempty; look at first evt and do the right thing
|
jtulach@1405
|
566 |
long currentTime, executionTime;
|
jtulach@1405
|
567 |
task = queue.getMin();
|
jtulach@1405
|
568 |
synchronized(task.lock) {
|
jtulach@1405
|
569 |
if (task.state == TimerTask.CANCELLED) {
|
jtulach@1405
|
570 |
queue.removeMin();
|
jtulach@1405
|
571 |
continue; // No action required, poll queue again
|
jtulach@1405
|
572 |
}
|
jtulach@1405
|
573 |
currentTime = System.currentTimeMillis();
|
jtulach@1405
|
574 |
executionTime = task.nextExecutionTime;
|
jtulach@1405
|
575 |
if (taskFired = (executionTime<=currentTime)) {
|
jtulach@1405
|
576 |
if (task.period == 0) { // Non-repeating, remove
|
jtulach@1405
|
577 |
queue.removeMin();
|
jtulach@1405
|
578 |
task.state = TimerTask.EXECUTED;
|
jtulach@1405
|
579 |
} else { // Repeating task, reschedule
|
jtulach@1405
|
580 |
queue.rescheduleMin(
|
jtulach@1405
|
581 |
task.period<0 ? currentTime - task.period
|
jtulach@1405
|
582 |
: executionTime + task.period);
|
jtulach@1405
|
583 |
}
|
jtulach@1405
|
584 |
}
|
jtulach@1405
|
585 |
}
|
jaroslav@1407
|
586 |
if (!taskFired) {
|
jaroslav@1407
|
587 |
// Task hasn't yet fired; wait
|
jaroslav@1407
|
588 |
notifyQueue((int)(executionTime - currentTime));
|
jaroslav@1407
|
589 |
return;
|
jaroslav@1407
|
590 |
}
|
jtulach@1405
|
591 |
}
|
jaroslav@1945
|
592 |
if (taskFired) {
|
jaroslav@1945
|
593 |
// Task fired; run it, holding no locks
|
jaroslav@1945
|
594 |
log("Running " + task);
|
jtulach@1405
|
595 |
task.run();
|
jaroslav@1945
|
596 |
log("Done running " + task);
|
jaroslav@1945
|
597 |
}
|
jaroslav@1407
|
598 |
} catch(Exception e) {
|
jaroslav@1407
|
599 |
e.printStackTrace();
|
jtulach@1405
|
600 |
}
|
jtulach@1405
|
601 |
}
|
jtulach@1405
|
602 |
}
|
jtulach@1405
|
603 |
}
|
jtulach@1405
|
604 |
|
jtulach@1405
|
605 |
/**
|
jtulach@1405
|
606 |
* This class represents a timer task queue: a priority queue of TimerTasks,
|
jtulach@1405
|
607 |
* ordered on nextExecutionTime. Each Timer object has one of these, which it
|
jtulach@1405
|
608 |
* shares with its TimerThread. Internally this class uses a heap, which
|
jtulach@1405
|
609 |
* offers log(n) performance for the add, removeMin and rescheduleMin
|
jtulach@1405
|
610 |
* operations, and constant time performance for the getMin operation.
|
jtulach@1405
|
611 |
*/
|
jtulach@1405
|
612 |
class TaskQueue {
|
jtulach@1405
|
613 |
/**
|
jtulach@1405
|
614 |
* Priority queue represented as a balanced binary heap: the two children
|
jtulach@1405
|
615 |
* of queue[n] are queue[2*n] and queue[2*n+1]. The priority queue is
|
jtulach@1405
|
616 |
* ordered on the nextExecutionTime field: The TimerTask with the lowest
|
jtulach@1405
|
617 |
* nextExecutionTime is in queue[1] (assuming the queue is nonempty). For
|
jtulach@1405
|
618 |
* each node n in the heap, and each descendant of n, d,
|
jtulach@1405
|
619 |
* n.nextExecutionTime <= d.nextExecutionTime.
|
jtulach@1405
|
620 |
*/
|
jtulach@1405
|
621 |
private TimerTask[] queue = new TimerTask[128];
|
jtulach@1405
|
622 |
|
jtulach@1405
|
623 |
/**
|
jtulach@1405
|
624 |
* The number of tasks in the priority queue. (The tasks are stored in
|
jtulach@1405
|
625 |
* queue[1] up to queue[size]).
|
jtulach@1405
|
626 |
*/
|
jtulach@1405
|
627 |
private int size = 0;
|
jtulach@1405
|
628 |
|
jtulach@1405
|
629 |
/**
|
jtulach@1405
|
630 |
* Returns the number of tasks currently on the queue.
|
jtulach@1405
|
631 |
*/
|
jtulach@1405
|
632 |
int size() {
|
jtulach@1405
|
633 |
return size;
|
jtulach@1405
|
634 |
}
|
jtulach@1405
|
635 |
|
jtulach@1405
|
636 |
/**
|
jtulach@1405
|
637 |
* Adds a new task to the priority queue.
|
jtulach@1405
|
638 |
*/
|
jtulach@1405
|
639 |
void add(TimerTask task) {
|
jtulach@1405
|
640 |
// Grow backing store if necessary
|
jtulach@1405
|
641 |
if (size + 1 == queue.length)
|
jtulach@1405
|
642 |
queue = Arrays.copyOf(queue, 2*queue.length);
|
jtulach@1405
|
643 |
|
jtulach@1405
|
644 |
queue[++size] = task;
|
jtulach@1405
|
645 |
fixUp(size);
|
jtulach@1405
|
646 |
}
|
jtulach@1405
|
647 |
|
jtulach@1405
|
648 |
/**
|
jtulach@1405
|
649 |
* Return the "head task" of the priority queue. (The head task is an
|
jtulach@1405
|
650 |
* task with the lowest nextExecutionTime.)
|
jtulach@1405
|
651 |
*/
|
jtulach@1405
|
652 |
TimerTask getMin() {
|
jtulach@1405
|
653 |
return queue[1];
|
jtulach@1405
|
654 |
}
|
jtulach@1405
|
655 |
|
jtulach@1405
|
656 |
/**
|
jtulach@1405
|
657 |
* Return the ith task in the priority queue, where i ranges from 1 (the
|
jtulach@1405
|
658 |
* head task, which is returned by getMin) to the number of tasks on the
|
jtulach@1405
|
659 |
* queue, inclusive.
|
jtulach@1405
|
660 |
*/
|
jtulach@1405
|
661 |
TimerTask get(int i) {
|
jtulach@1405
|
662 |
return queue[i];
|
jtulach@1405
|
663 |
}
|
jtulach@1405
|
664 |
|
jtulach@1405
|
665 |
/**
|
jtulach@1405
|
666 |
* Remove the head task from the priority queue.
|
jtulach@1405
|
667 |
*/
|
jtulach@1405
|
668 |
void removeMin() {
|
jtulach@1405
|
669 |
queue[1] = queue[size];
|
jtulach@1405
|
670 |
queue[size--] = null; // Drop extra reference to prevent memory leak
|
jtulach@1405
|
671 |
fixDown(1);
|
jtulach@1405
|
672 |
}
|
jtulach@1405
|
673 |
|
jtulach@1405
|
674 |
/**
|
jtulach@1405
|
675 |
* Removes the ith element from queue without regard for maintaining
|
jtulach@1405
|
676 |
* the heap invariant. Recall that queue is one-based, so
|
jtulach@1405
|
677 |
* 1 <= i <= size.
|
jtulach@1405
|
678 |
*/
|
jtulach@1405
|
679 |
void quickRemove(int i) {
|
jtulach@1405
|
680 |
assert i <= size;
|
jtulach@1405
|
681 |
|
jtulach@1405
|
682 |
queue[i] = queue[size];
|
jtulach@1405
|
683 |
queue[size--] = null; // Drop extra ref to prevent memory leak
|
jtulach@1405
|
684 |
}
|
jtulach@1405
|
685 |
|
jtulach@1405
|
686 |
/**
|
jtulach@1405
|
687 |
* Sets the nextExecutionTime associated with the head task to the
|
jtulach@1405
|
688 |
* specified value, and adjusts priority queue accordingly.
|
jtulach@1405
|
689 |
*/
|
jtulach@1405
|
690 |
void rescheduleMin(long newTime) {
|
jtulach@1405
|
691 |
queue[1].nextExecutionTime = newTime;
|
jtulach@1405
|
692 |
fixDown(1);
|
jtulach@1405
|
693 |
}
|
jtulach@1405
|
694 |
|
jtulach@1405
|
695 |
/**
|
jtulach@1405
|
696 |
* Returns true if the priority queue contains no elements.
|
jtulach@1405
|
697 |
*/
|
jtulach@1405
|
698 |
boolean isEmpty() {
|
jtulach@1405
|
699 |
return size==0;
|
jtulach@1405
|
700 |
}
|
jtulach@1405
|
701 |
|
jtulach@1405
|
702 |
/**
|
jtulach@1405
|
703 |
* Removes all elements from the priority queue.
|
jtulach@1405
|
704 |
*/
|
jtulach@1405
|
705 |
void clear() {
|
jtulach@1405
|
706 |
// Null out task references to prevent memory leak
|
jtulach@1405
|
707 |
for (int i=1; i<=size; i++)
|
jtulach@1405
|
708 |
queue[i] = null;
|
jtulach@1405
|
709 |
|
jtulach@1405
|
710 |
size = 0;
|
jtulach@1405
|
711 |
}
|
jtulach@1405
|
712 |
|
jtulach@1405
|
713 |
/**
|
jtulach@1405
|
714 |
* Establishes the heap invariant (described above) assuming the heap
|
jtulach@1405
|
715 |
* satisfies the invariant except possibly for the leaf-node indexed by k
|
jtulach@1405
|
716 |
* (which may have a nextExecutionTime less than its parent's).
|
jtulach@1405
|
717 |
*
|
jtulach@1405
|
718 |
* This method functions by "promoting" queue[k] up the hierarchy
|
jtulach@1405
|
719 |
* (by swapping it with its parent) repeatedly until queue[k]'s
|
jtulach@1405
|
720 |
* nextExecutionTime is greater than or equal to that of its parent.
|
jtulach@1405
|
721 |
*/
|
jtulach@1405
|
722 |
private void fixUp(int k) {
|
jtulach@1405
|
723 |
while (k > 1) {
|
jtulach@1405
|
724 |
int j = k >> 1;
|
jtulach@1405
|
725 |
if (queue[j].nextExecutionTime <= queue[k].nextExecutionTime)
|
jtulach@1405
|
726 |
break;
|
jtulach@1405
|
727 |
TimerTask tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
|
jtulach@1405
|
728 |
k = j;
|
jtulach@1405
|
729 |
}
|
jtulach@1405
|
730 |
}
|
jtulach@1405
|
731 |
|
jtulach@1405
|
732 |
/**
|
jtulach@1405
|
733 |
* Establishes the heap invariant (described above) in the subtree
|
jtulach@1405
|
734 |
* rooted at k, which is assumed to satisfy the heap invariant except
|
jtulach@1405
|
735 |
* possibly for node k itself (which may have a nextExecutionTime greater
|
jtulach@1405
|
736 |
* than its children's).
|
jtulach@1405
|
737 |
*
|
jtulach@1405
|
738 |
* This method functions by "demoting" queue[k] down the hierarchy
|
jtulach@1405
|
739 |
* (by swapping it with its smaller child) repeatedly until queue[k]'s
|
jtulach@1405
|
740 |
* nextExecutionTime is less than or equal to those of its children.
|
jtulach@1405
|
741 |
*/
|
jtulach@1405
|
742 |
private void fixDown(int k) {
|
jtulach@1405
|
743 |
int j;
|
jtulach@1405
|
744 |
while ((j = k << 1) <= size && j > 0) {
|
jtulach@1405
|
745 |
if (j < size &&
|
jtulach@1405
|
746 |
queue[j].nextExecutionTime > queue[j+1].nextExecutionTime)
|
jtulach@1405
|
747 |
j++; // j indexes smallest kid
|
jtulach@1405
|
748 |
if (queue[k].nextExecutionTime <= queue[j].nextExecutionTime)
|
jtulach@1405
|
749 |
break;
|
jtulach@1405
|
750 |
TimerTask tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
|
jtulach@1405
|
751 |
k = j;
|
jtulach@1405
|
752 |
}
|
jtulach@1405
|
753 |
}
|
jtulach@1405
|
754 |
|
jtulach@1405
|
755 |
/**
|
jtulach@1405
|
756 |
* Establishes the heap invariant (described above) in the entire tree,
|
jtulach@1405
|
757 |
* assuming nothing about the order of the elements prior to the call.
|
jtulach@1405
|
758 |
*/
|
jtulach@1405
|
759 |
void heapify() {
|
jtulach@1405
|
760 |
for (int i = size/2; i >= 1; i--)
|
jtulach@1405
|
761 |
fixDown(i);
|
jtulach@1405
|
762 |
}
|
jtulach@1405
|
763 |
}
|