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Diffstat (limited to 'libjava/classpath/java/lang/ref/PhantomReference.java')
-rw-r--r-- | libjava/classpath/java/lang/ref/PhantomReference.java | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/libjava/classpath/java/lang/ref/PhantomReference.java b/libjava/classpath/java/lang/ref/PhantomReference.java new file mode 100644 index 000000000..29215ead7 --- /dev/null +++ b/libjava/classpath/java/lang/ref/PhantomReference.java @@ -0,0 +1,73 @@ +/* java.lang.ref.PhantomReference + Copyright (C) 1999, 2004 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; + +/** + * A phantom reference is useful, to get notified, when an object got + * finalized. You can't access that object though, since it is + * finalized. This is the reason, why <code>get()</code> always + * returns null. + * + * @author Jochen Hoenicke + */ +public class PhantomReference<T> + extends Reference<T> +{ + /** + * Creates a new phantom reference. + * @param referent the object that should be watched. + * @param q the queue that should be notified, if the referent was + * finalized. This mustn't be <code>null</code>. + * @exception NullPointerException if q is null. + */ + public PhantomReference(T referent, ReferenceQueue<? super T> q) + { + super(referent, q); + } + + /** + * Returns the object, this reference refers to. + * @return <code>null</code>, since the refered object may be + * finalized and thus not accessible. + */ + public T get() + { + return null; + } +} |