From 6ba7ed48f50f5ebb1d9568f8b010cee60a5fd480 Mon Sep 17 00:00:00 2001 From: bryce Date: Mon, 11 Dec 2000 03:47:48 +0000 Subject: * Makefile.am: Add HashSet.java and java/lang/ref classes. Remove BasicMapEntry.java and Bucket.java. * Makefile.in: Rebuilt. * java/util/HashMap.java: Rewritten. * java/util/HashSet.java: Imported from classpath. * java/util/WeakHashMap.java: Imported from classpath. * java/util/Hashtable.java: Rewritten based on new HashMap code. * java/util/Bucket.java: Deleted. * java/util/BasicMapEntry.java: Deleted. * java/util/Collections.java (search): Use a for-loop, not iterator hasNext(). (copy): Use a for-loop. Throw an IndexOutOfBoundsException if run out of elements in source. (max): Use a for-loop. (min): Ditto. (reverse): Keep track of positions instead of using Iterator's nextIndex() and previousIndex(). (shuffle(List)): Initialize defaultRandom if required using double-check thread safety idiom. Call two-argument shuffle method using defaultRandom. (defaultRandom): New field. (shuffle(List, Random)): Use a for-loop. Keep track of pos instead of using previousIndex() and nextIndex(). (singletonMap(iterator)): Use a HashMap.Entry, not BasicMapEntry. * java/util/AbstractCollection.java (toString): Use a StringBuffer. * java/util/AbstractMap.java (toString): Use StringBuffer. * java/lang/ref/PhantomReference.java: Imported from classpath. * java/lang/ref/SoftReference.java: Ditto. * java/lang/ref/Reference.java: Ditto. * java/lang/ref/WeakReference.java: Ditto. * java/lang/ref/ReferenceQueue.java: Ditto. git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@38183 138bc75d-0d04-0410-961f-82ee72b054a4 --- libjava/java/lang/ref/ReferenceQueue.java | 134 ++++++++++++++++++++++++++++++ 1 file changed, 134 insertions(+) create mode 100644 libjava/java/lang/ref/ReferenceQueue.java (limited to 'libjava/java/lang/ref/ReferenceQueue.java') diff --git a/libjava/java/lang/ref/ReferenceQueue.java b/libjava/java/lang/ref/ReferenceQueue.java new file mode 100644 index 00000000000..57ec4193db1 --- /dev/null +++ b/libjava/java/lang/ref/ReferenceQueue.java @@ -0,0 +1,134 @@ +/* java.lang.ref.ReferenceQueue + Copyright (C) 1999 Free Software Foundation, Inc. + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA +02111-1307 USA. + +As a special exception, if you link this library with other files to +produce an executable, this library does not by itself cause the +resulting executable to be covered by the GNU General Public License. +This exception does not however invalidate any other reasons why the +executable file might be covered by the GNU General Public License. */ + + +package java.lang.ref; + +/** + * This is the queue, where references can enqueue themselve on. Each + * reference may be registered to a queue at initialization time and + * will be appended to the queue, when the enqueue method is called. + * + * The enqueue method may be automatically called by the garbage + * collector if it detects, that the object is only reachable through + * the Reference objects. + * + * @author Jochen Hoenicke + * @see Reference#enqueue() + */ +public class ReferenceQueue +{ + /** + * This is a linked list of references. If this is null, the list is + * empty. Otherwise this points to the first reference on the queue. + * The first reference will point to the next reference via the + * nextOnQueue field. The last reference will point to + * itself (not to null, since nextOnQueue is used to + * determine if a reference is enqueued). + */ + private Reference first; + + /** + * Creates a new empty reference queue. + */ + public ReferenceQueue() + { + } + + /** + * Checks if there is a reference on the queue, returning it + * immediately. The reference will be dequeued. + * + * @return a reference on the queue, if there is one, + * null otherwise. + */ + public synchronized Reference poll() + { + return dequeue(); + } + + /** + * This is called by reference to enqueue itself on this queue. + * @param ref the reference that should be enqueued. + */ + synchronized void enqueue(Reference ref) + { + /* last reference will point to itself */ + ref.nextOnQueue = first == null ? ref : first; + first = ref; + /* this wakes only one remove thread. */ + notify(); + } + + /** + * Remove a reference from the queue, if there is one. + * @return the first element of the queue, or null if there isn't any. + */ + private Reference dequeue() + { + if (first == null) + return null; + + Reference result = first; + first = (first == first.nextOnQueue) ? null : first.nextOnQueue; + result.nextOnQueue = null; + return result; + } + + /** + * Removes a reference from the queue, blocking for timeout + * until a reference is enqueued. + * @param timeout the timeout period in milliseconds, 0 means + * wait forever. + * @return the reference removed from the queue, or + * null if timeout period expired. + * @exception InterruptedException if the wait was interrupted. + */ + public synchronized Reference remove(long timeout) + throws InterruptedException + { + if (first == null) + { + wait(timeout); + } + + return dequeue(); + } + + + /** + * Removes a reference from the queue, blocking until a reference is + * enqueued. + * + * @return the reference removed from the queue. + * @exception InterruptedException if the wait was interrupted. + */ + public Reference remove() + throws InterruptedException + { + return remove(0L); + } +} -- cgit v1.2.1