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25 
26 package 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  */
53 public 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      */
EventListenerProxy(T listener)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      */
getListener()72     public T getListener() {
73         return this.listener;
74     }
75 }
76