jdk/src/share/classes/java/util/EventListenerProxy.java

/*
 * Copyright 2000-2004 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
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 */

package java.util;

/**
 * An abstract wrapper class for an {@code EventListener} class
 * which associates a set of additional parameters with the listener.
 * Subclasses must provide the storage and accessor methods
 * for the additional arguments or parameters.
 * <p>
 * For example, a bean which supports named properties
 * would have a two argument method signature for adding
 * a {@code PropertyChangeListener} for a property:
 * <pre>
 * public void addPropertyChangeListener(String propertyName,
 *                                       PropertyChangeListener listener)
 * </pre>
 * If the bean also implemented the zero argument get listener method:
 * <pre>
 * public PropertyChangeListener[] getPropertyChangeListeners()
 * </pre>
 * then the array may contain inner {@code PropertyChangeListeners}
 * which are also {@code PropertyChangeListenerProxy} objects.
 * <p>
 * If the calling method is interested in retrieving the named property
 * then it would have to test the element to see if it is a proxy class.
 *
 * @since 1.4
 */
public abstract class EventListenerProxy<T extends EventListener>
        implements EventListener {

    private final T listener;

    /**
     * Creates a proxy for the specified listener.
     *
     * @param listener  the listener object
     */
    public EventListenerProxy(T listener) {
        this.listener = listener;
    }

    /**
     * Returns the listener associated with the proxy.
     *
     * @return  the listener associated with the proxy
     */
    public T getListener() {
        return this.listener;
    }
}