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1 /*
2 * Copyright (c) 2003 Scott Howlett & Paul Libbrecht.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in
14 * the documentation and/or other materials provided with the
15 * distribution.
16 *
17 * 3. The end-user documentation included with the redistribution,
18 * if any, must include the following acknowledgment:
19 * "This product includes software developed by the Xwing
20 * Project ( http://xwing.sourceforge.net/ )."
21 * Alternately, this acknowledgment may appear in the software itself,
22 * if and wherever such third-party acknowledgments normally appear.
23 *
24 * 4. The name "Xwing" must not be used to endorse or promote products
25 * derived from this software without prior written permission. For
26 * written permission, please contact the project authors via
27 * the Xwing project site, http://xwing.sourceforge.net/ .
28 *
29 * 5. Products derived from this software may not be called "Xwing",
30 * nor may "Xwing" appear in their name, without prior written
31 * permission of the Xwing project.
32 *
33 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
34 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
35 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
36 * DISCLAIMED. IN NO EVENT SHALL THE XWING AUTHORS OR THE PROJECT
37 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
38 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
39 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
40 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
41 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
42 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
43 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
44 * SUCH DAMAGE.
45 *
46 * For more information on Xwing, please see
47 * < http://xwing.sourceforge.net/ >.
48 */
49
50 package net.sourceforge.xwing;
51
52 import java.lang.ref.WeakReference;
53
54 import javax.swing.event.ChangeEvent;
55 import javax.swing.event.ChangeListener;
56
57
58 /***
59 * A SourceSink that acts as a proxy to another SourceSink.
60 * The change listener that attaches the other SourceSink back
61 * to this one is implemented via a WeakReference so that this
62 * SourceSink may be garbage collected even if the other SourceSink
63 * is still reachable.
64 *
65 * @author Scott Howlett
66 * @version $Revision: 1.2 $
67 */
68
69 public class WeakSourceSink extends AbstractSourceSink {
70
71 private SourceSink srcSink;
72
73 /***
74 * Create a new WeakSourceSink.
75 * @param ss the SourceSink that values are read from and written to.
76 */
77
78 public WeakSourceSink(SourceSink ss) {
79 srcSink = ss;
80 Listener.connect(srcSink, this);
81 }
82
83 public Object get() {
84 return srcSink.get();
85 }
86
87 public void set(Object newValue) {
88 srcSink.set(newValue);
89 }
90
91 }
92
93 class Listener implements ChangeListener {
94
95 private SourceSink src;
96 private WeakReference targetRef;
97
98 private Listener(SourceSink src, SourceSink target) {
99 targetRef = new WeakReference(target);
100 }
101
102 public void stateChanged(ChangeEvent e) {
103 ChangeListener target = (ChangeListener) targetRef.get();
104 if (target != null) {
105 target.stateChanged(e);
106 } else {
107 src.removeChangeListener(this);
108 }
109 }
110
111 public static void connect(SourceSink src, SourceSink target) {
112 src.addChangeListener(new Listener(src, target));
113 }
114 }
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