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Diffstat (limited to 'libjava/classpath/java/lang/ref/ReferenceQueue.java')
-rw-r--r-- | libjava/classpath/java/lang/ref/ReferenceQueue.java | 164 |
1 files changed, 0 insertions, 164 deletions
diff --git a/libjava/classpath/java/lang/ref/ReferenceQueue.java b/libjava/classpath/java/lang/ref/ReferenceQueue.java deleted file mode 100644 index 73f62d6..0000000 --- a/libjava/classpath/java/lang/ref/ReferenceQueue.java +++ /dev/null @@ -1,164 +0,0 @@ -/* java.lang.ref.ReferenceQueue - Copyright (C) 1999, 2004, 2006 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., 51 Franklin Street, Fifth Floor, Boston, MA -02110-1301 USA. - -Linking this library statically or dynamically with other modules is -making a combined work based on this library. Thus, the terms and -conditions of the GNU General Public License cover the whole -combination. - -As a special exception, the copyright holders of this library give you -permission to link this library with independent modules to produce an -executable, regardless of the license terms of these independent -modules, and to copy and distribute the resulting executable under -terms of your choice, provided that you also meet, for each linked -independent module, the terms and conditions of the license of that -module. An independent module is a module which is not derived from -or based on this library. If you modify this library, you may extend -this exception to your version of the library, but you are not -obligated to do so. If you do not wish to do so, delete this -exception statement from your version. */ - - -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<T> -{ - /** - * 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 - * <code>nextOnQueue</code> field. The last reference will point to - * itself (not to null, since <code>nextOnQueue</code> is used to - * determine if a reference is enqueued). - */ - private Reference<? extends T> first; - - /** - * This is the lock that protects our linked list and is used to signal - * a thread waiting in remove(). - */ - private final Object lock = new Object(); - - /** - * 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, - * <code>null</code> otherwise. - */ - public Reference<? extends T> poll() - { - return dequeue(); - } - - /** - * This is called by reference to enqueue itself on this queue. - * @param ref the reference that should be enqueued. - * @return true if successful, false if not. - */ - final boolean enqueue(Reference<? extends T> ref) - { - synchronized (lock) - { - if (ref.queue != this) - return false; - - /* last reference will point to itself */ - ref.nextOnQueue = first == null ? ref : first; - ref.queue = null; - first = ref; - /* this wakes only one remove thread. */ - lock.notify(); - return true; - } - } - - /** - * 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<? extends T> dequeue() - { - synchronized (lock) - { - if (first == null) - return null; - - Reference<? extends T> result = first; - first = (first == first.nextOnQueue) ? null : first.nextOnQueue; - result.nextOnQueue = null; - return result; - } - } - - /** - * Removes a reference from the queue, blocking for <code>timeout</code> - * until a reference is enqueued. - * @param timeout the timeout period in milliseconds, <code>0</code> means - * wait forever. - * @return the reference removed from the queue, or - * <code>null</code> if timeout period expired. - * @exception InterruptedException if the wait was interrupted. - */ - public Reference<? extends T> remove(long timeout) - throws InterruptedException - { - synchronized (lock) - { - if (first == null) - lock.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<? extends T> remove() - throws InterruptedException - { - return remove(0L); - } -} |