1 /*
2 * Copyright (c) 1997, 2003, Oracle and/or its affiliates. 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * 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 {@code null} if registration is not required
67 */
68 public WeakReference(T referent, ReferenceQueue<? super T> q) {
69 super(referent, q);
70 }
71
72 }
|
1 /*
2 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * 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 * <p>
34 * The referent must not be an instance of a primitive class; such a value
35 * can never have another reference to it and cannot be held in a reference type.
36 *
37 * <p> Suppose that the garbage collector determines at a certain point in time
38 * that an object is <a href="package-summary.html#reachability">weakly
39 * reachable</a>. At that time it will atomically clear all weak references to
40 * that object and all weak references to any other weakly-reachable objects
41 * from which that object is reachable through a chain of strong and soft
42 * references. At the same time it will declare all of the formerly
43 * weakly-reachable objects to be finalizable. At the same time or at some
44 * later time it will enqueue those newly-cleared weak references that are
45 * registered with reference queues.
46 *
47 * @author Mark Reinhold
48 * @since 1.2
49 */
50
51 public class WeakReference<T> extends Reference<T> {
52
53 /**
54 * Creates a new weak reference that refers to the given object. The new
55 * reference is not registered with any queue.
56 *
57 * @param referent object the new weak reference will refer to
58 * @throws IllegalArgumentException if the referent is an instance of a
59 * {@link Class#isPrimitiveClass() primitive class}
60 */
61 public WeakReference(T referent) {
62 super(referent);
63 }
64
65 /**
66 * Creates a new weak reference that refers to the given object and is
67 * registered with the given queue.
68 *
69 * @param referent object the new weak reference will refer to
70 * @param q the queue with which the reference is to be registered,
71 * or {@code null} if registration is not required
72 * @throws IllegalArgumentException if the referent is an instance of a
73 * {@link Class#isPrimitiveClass() primitive class}
74 */
75 public WeakReference(T referent, ReferenceQueue<? super T> q) {
76 super(referent, q);
77 }
78
79 }
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