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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/java/lang/ref/PhantomReference.java
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+/* 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;
+ }
+}