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74 lines
2.6 KiB
Java
74 lines
2.6 KiB
Java
/* java.lang.ref.PhantomReference
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Copyright (C) 1999 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.lang.ref;
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/**
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* A phantom reference is useful, to get notified, when an object got
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* finalized. You can't access that object though, since it is
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* finalized. This is the reason, why <code>get()</code> always
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* returns null.
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*
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* @author Jochen Hoenicke
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*/
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public class PhantomReference
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extends Reference
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{
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/**
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* Creates a new phantom reference.
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* @param referent the object that should be watched.
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* @param q the queue that should be notified, if the referent was
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* finalized. This mustn't be <code>null</code>.
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* @exception NullPointerException if q is null.
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*/
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public PhantomReference(Object referent, ReferenceQueue q)
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{
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super(referent, q);
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}
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/**
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* Returns the object, this reference refers to.
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* @return <code>null</code>, since the refered object may be
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* finalized and thus not accessible.
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*/
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public Object get()
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{
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return null;
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}
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}
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