EventListenerProxy.java revision 49965c1dc9da104344f4893a05e45795a5740d20 
1/*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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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 *
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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24 */
25
26package java.util;
27
28/**
29 * An abstract wrapper class for an {@code EventListener} class
30 * which associates a set of additional parameters with the listener.
31 * Subclasses must provide the storage and accessor methods
32 * for the additional arguments or parameters.
33 * <p>
34 * For example, a bean which supports named properties
35 * would have a two argument method signature for adding
36 * a {@code PropertyChangeListener} for a property:
37 * <pre>
38 * public void addPropertyChangeListener(String propertyName,
39 *                                       PropertyChangeListener listener)
40 * </pre>
41 * If the bean also implemented the zero argument get listener method:
42 * <pre>
43 * public PropertyChangeListener[] getPropertyChangeListeners()
44 * </pre>
45 * then the array may contain inner {@code PropertyChangeListeners}
46 * which are also {@code PropertyChangeListenerProxy} objects.
47 * <p>
48 * If the calling method is interested in retrieving the named property
49 * then it would have to test the element to see if it is a proxy class.
50 *
51 * @since 1.4
52 */
53public abstract class EventListenerProxy<T extends EventListener>
54        implements EventListener {
55
56    private final T listener;
57
58    /**
59     * Creates a proxy for the specified listener.
60     *
61     * @param listener  the listener object
62     */
63    public EventListenerProxy(T listener) {
64        this.listener = listener;
65    }
66
67    /**
68     * Returns the listener associated with the proxy.
69     *
70     * @return  the listener associated with the proxy
71     */
72    public T getListener() {
73        return this.listener;
74    }
75}
76