1.1 --- a/emul/compact/src/main/java/java/lang/ref/PhantomReference.java Fri Mar 22 16:59:47 2013 +0100
1.2 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000
1.3 @@ -1,83 +0,0 @@
1.4 -/*
1.5 - * Copyright (c) 1997, 2003, Oracle and/or its affiliates. All rights reserved.
1.6 - * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 - *
1.8 - * This code is free software; you can redistribute it and/or modify it
1.9 - * under the terms of the GNU General Public License version 2 only, as
1.10 - * published by the Free Software Foundation. Oracle designates this
1.11 - * particular file as subject to the "Classpath" exception as provided
1.12 - * by Oracle in the LICENSE file that accompanied this code.
1.13 - *
1.14 - * This code is distributed in the hope that it will be useful, but WITHOUT
1.15 - * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.16 - * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.17 - * version 2 for more details (a copy is included in the LICENSE file that
1.18 - * accompanied this code).
1.19 - *
1.20 - * You should have received a copy of the GNU General Public License version
1.21 - * 2 along with this work; if not, write to the Free Software Foundation,
1.22 - * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.23 - *
1.24 - * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.25 - * or visit www.oracle.com if you need additional information or have any
1.26 - * questions.
1.27 - */
1.28 -
1.29 -package java.lang.ref;
1.30 -
1.31 -
1.32 -/**
1.33 - * Phantom reference objects, which are enqueued after the collector
1.34 - * determines that their referents may otherwise be reclaimed. Phantom
1.35 - * references are most often used for scheduling pre-mortem cleanup actions in
1.36 - * a more flexible way than is possible with the Java finalization mechanism.
1.37 - *
1.38 - * <p> If the garbage collector determines at a certain point in time that the
1.39 - * referent of a phantom reference is <a
1.40 - * href="package-summary.html#reachability">phantom reachable</a>, then at that
1.41 - * time or at some later time it will enqueue the reference.
1.42 - *
1.43 - * <p> In order to ensure that a reclaimable object remains so, the referent of
1.44 - * a phantom reference may not be retrieved: The <code>get</code> method of a
1.45 - * phantom reference always returns <code>null</code>.
1.46 - *
1.47 - * <p> Unlike soft and weak references, phantom references are not
1.48 - * automatically cleared by the garbage collector as they are enqueued. An
1.49 - * object that is reachable via phantom references will remain so until all
1.50 - * such references are cleared or themselves become unreachable.
1.51 - *
1.52 - * @author Mark Reinhold
1.53 - * @since 1.2
1.54 - */
1.55 -
1.56 -public class PhantomReference<T> extends Reference<T> {
1.57 -
1.58 - /**
1.59 - * Returns this reference object's referent. Because the referent of a
1.60 - * phantom reference is always inaccessible, this method always returns
1.61 - * <code>null</code>.
1.62 - *
1.63 - * @return <code>null</code>
1.64 - */
1.65 - public T get() {
1.66 - return null;
1.67 - }
1.68 -
1.69 - /**
1.70 - * Creates a new phantom reference that refers to the given object and
1.71 - * is registered with the given queue.
1.72 - *
1.73 - * <p> It is possible to create a phantom reference with a <tt>null</tt>
1.74 - * queue, but such a reference is completely useless: Its <tt>get</tt>
1.75 - * method will always return null and, since it does not have a queue, it
1.76 - * will never be enqueued.
1.77 - *
1.78 - * @param referent the object the new phantom reference will refer to
1.79 - * @param q the queue with which the reference is to be registered,
1.80 - * or <tt>null</tt> if registration is not required
1.81 - */
1.82 - public PhantomReference(T referent, ReferenceQueue<? super T> q) {
1.83 - super(referent, q);
1.84 - }
1.85 -
1.86 -}