1 /*

     2  * Copyright 1997-2003 Sun Microsystems, Inc.  All Rights Reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Sun designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Sun in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    22  * CA 95054 USA or visit www.sun.com if you need additional information or

    23  * have any questions.

    24  */

    25 

    26 package java.lang.ref;

    27 

    28 

    29 /**

    30  * Weak reference objects, which do not prevent their referents from being

    31  * made finalizable, finalized, and then reclaimed.  Weak references are most

    32  * often used to implement canonicalizing mappings.

    33  *

    34  * <p> Suppose that the garbage collector determines at a certain point in time

    35  * that an object is <a href="package-summary.html#reachability">weakly

    36  * reachable</a>.  At that time it will atomically clear all weak references to

    37  * that object and all weak references to any other weakly-reachable objects

    38  * from which that object is reachable through a chain of strong and soft

    39  * references.  At the same time it will declare all of the formerly

    40  * weakly-reachable objects to be finalizable.  At the same time or at some

    41  * later time it will enqueue those newly-cleared weak references that are

    42  * registered with reference queues.

    43  *

    44  * @author   Mark Reinhold

    45  * @since    1.2

    46  */

    47 

    48 public class WeakReference<T> extends Reference<T> {

    49 

    50     /**

    51      * Creates a new weak reference that refers to the given object.  The new

    52      * reference is not registered with any queue.

    53      *

    54      * @param referent object the new weak reference will refer to

    55      */

    56     public WeakReference(T referent) {

    57         super(referent);

    58     }

    59 

    60     /**

    61      * Creates a new weak reference that refers to the given object and is

    62      * registered with the given queue.

    63      *

    64      * @param referent object the new weak reference will refer to

    65      * @param q the queue with which the reference is to be registered,

    66      *          or <tt>null</tt> if registration is not required

    67      */

    68     public WeakReference(T referent, ReferenceQueue<? super T> q) {

    69         super(referent, q);

    70     }

    71 

    72 }