jdk/src/java.base/share/classes/java/lang/ref/WeakReference.java
author psandoz
Tue, 06 Oct 2015 18:42:06 +0200
changeset 35254 ba6a26f39b86
parent 32033 bf24e33c7919
permissions -rw-r--r--
8133348: Reference.reachabilityFence Reviewed-by: plevart, mr, chegar, mchung Contributed-by: dl@cs.oswego.edu, aleksey.shipilev@oracle.com, paul.sandoz@oracle.com
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/*
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 * Copyright (c) 1997, 2003, 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.lang.ref;
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/**
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 * Weak reference objects, which do not prevent their referents from being
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 * made finalizable, finalized, and then reclaimed.  Weak references are most
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 * often used to implement canonicalizing mappings.
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 *
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 * <p> Suppose that the garbage collector determines at a certain point in time
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 * that an object is <a href="package-summary.html#reachability">weakly
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 * reachable</a>.  At that time it will atomically clear all weak references to
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 * that object and all weak references to any other weakly-reachable objects
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 * from which that object is reachable through a chain of strong and soft
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 * references.  At the same time it will declare all of the formerly
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 * weakly-reachable objects to be finalizable.  At the same time or at some
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 * later time it will enqueue those newly-cleared weak references that are
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 * registered with reference queues.
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 *
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 * @author   Mark Reinhold
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 * @since    1.2
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 */
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public class WeakReference<T> extends Reference<T> {
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    /**
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     * Creates a new weak reference that refers to the given object.  The new
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     * reference is not registered with any queue.
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     *
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     * @param referent object the new weak reference will refer to
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     */
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    public WeakReference(T referent) {
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        super(referent);
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    }
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    /**
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     * Creates a new weak reference that refers to the given object and is
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     * registered with the given queue.
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     *
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     * @param referent object the new weak reference will refer to
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     * @param q the queue with which the reference is to be registered,
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     *          or {@code null} if registration is not required
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     */
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    public WeakReference(T referent, ReferenceQueue<? super T> q) {
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        super(referent, q);
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    }
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}