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8263903: Use Cleaner instead of finalize to auto stop Timer thread

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Reviewed-by: dholmes, alanb, bchristi, rriggs, mchung
This commit is contained in:
Kim Barrett 2021-03-23 21:16:35 +00:00
parent 35102cb03f
commit 2425462a84
2 changed files with 108 additions and 14 deletions
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38
src/java.base/share/classes/java/util/Timer.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1999, 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -26,6 +26,8 @@
package java.util;
import java.util.Date;
import java.util.concurrent.atomic.AtomicInteger;
import java.lang.ref.Cleaner.Cleanable;
import jdk.internal.ref.CleanerFactory;
/**
* A facility for threads to schedule tasks for future execution in a
@ -101,21 +103,29 @@ public class Timer {
private final TimerThread thread = new TimerThread(queue);
/**
* This object causes the timer's task execution thread to exit
* gracefully when there are no live references to the Timer object and no
* tasks in the timer queue. It is used in preference to a finalizer on
* Timer as such a finalizer would be susceptible to a subclass's
* finalizer forgetting to call it.
* An object of this class is registered with a Cleaner as the cleanup
* handler for this Timer object. This causes the execution thread to
* exit gracefully when there are no live references to the Timer object
* and no tasks in the timer queue.
*/
private final Object threadReaper = new Object() {
@SuppressWarnings("deprecation")
protected void finalize() throws Throwable {
private static class ThreadReaper implements Runnable {
private final TaskQueue queue;
private final TimerThread thread;
ThreadReaper(TaskQueue queue, TimerThread thread) {
this.queue = queue;
this.thread = thread;
}
public void run() {
synchronized(queue) {
thread.newTasksMayBeScheduled = false;
queue.notify(); // In case queue is empty.
}
}
};
}
private final Cleanable cleanup;
/**
* This ID is used to generate thread names.
@ -157,8 +167,7 @@ public class Timer {
* @since 1.5
*/
public Timer(String name) {
thread.setName(name);
thread.start();
this(name, false);
}
/**
@ -172,6 +181,8 @@ public class Timer {
* @since 1.5
*/
public Timer(String name, boolean isDaemon) {
var threadReaper = new ThreadReaper(queue, thread);
this.cleanup = CleanerFactory.cleaner().register(this, threadReaper);
thread.setName(name);
thread.setDaemon(isDaemon);
thread.start();
@ -428,9 +439,8 @@ public class Timer {
*/
public void cancel() {
synchronized(queue) {
thread.newTasksMayBeScheduled = false;
queue.clear();
queue.notify(); // In case queue was already empty.
cleanup.clean();
}
}