author | psandoz |
Tue, 06 Oct 2015 18:42:06 +0200 | |
changeset 35254 | ba6a26f39b86 |
parent 32033 | bf24e33c7919 |
child 35265 | 87b434f45259 |
permissions | -rw-r--r-- |
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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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* Phantom reference objects, which are enqueued after the collector |
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* determines that their referents may otherwise be reclaimed. Phantom |
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* references are most often used for scheduling pre-mortem cleanup actions in |
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* a more flexible way than is possible with the Java finalization mechanism. |
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* |
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* <p> If the garbage collector determines at a certain point in time that the |
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* referent of a phantom reference is <a |
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* href="package-summary.html#reachability">phantom reachable</a>, then at that |
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* time or at some later time it will enqueue the reference. |
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* |
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* <p> In order to ensure that a reclaimable object remains so, the referent of |
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bf24e33c7919
8132468: docs: replace <tt> tags (obsolete in html5) for java.io, java.lang, java.math
avstepan
parents:
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* a phantom reference may not be retrieved: The {@code get} method of a |
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8132468: docs: replace <tt> tags (obsolete in html5) for java.io, java.lang, java.math
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parents:
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* phantom reference always returns {@code null}. |
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* |
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* <p> Unlike soft and weak references, phantom references are not |
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* automatically cleared by the garbage collector as they are enqueued. An |
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* object that is reachable via phantom references will remain so until all |
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* such references are cleared or themselves become unreachable. |
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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 PhantomReference<T> extends Reference<T> { |
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/** |
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* Returns this reference object's referent. Because the referent of a |
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* phantom reference is always inaccessible, this method always returns |
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8132468: docs: replace <tt> tags (obsolete in html5) for java.io, java.lang, java.math
avstepan
parents:
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diff
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* {@code null}. |
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* |
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* @return {@code null} |
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*/ |
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public T get() { |
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return null; |
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} |
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/** |
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* Creates a new phantom reference that refers to the given object and |
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* is registered with the given queue. |
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* |
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8132468: docs: replace <tt> tags (obsolete in html5) for java.io, java.lang, java.math
avstepan
parents:
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* <p> It is possible to create a phantom reference with a {@code null} |
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8132468: docs: replace <tt> tags (obsolete in html5) for java.io, java.lang, java.math
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* queue, but such a reference is completely useless: Its {@code get} |
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* method will always return null and, since it does not have a queue, it |
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* will never be enqueued. |
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* |
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* @param referent the object the new phantom reference will refer to |
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* @param q the queue with which the reference is to be registered, |
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avstepan
parents:
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* or {@code null} if registration is not required |
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*/ |
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public PhantomReference(T referent, ReferenceQueue<? super T> q) { |
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super(referent, q); |
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} |
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} |