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 * Copyright (c) 2011, 2013, Oracle and/or its affiliates. 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle 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.
 *
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package com.sun.javafx.beans.event;

import javafx.beans.InvalidationListener;
import javafx.beans.WeakInvalidationListener;

A helper base class for notify listeners. It holds reference to its WeakListener wrapper. 
 Without this class, an observer which uses weak listeners would need to hold two references. The first to the original ChangeListener to prevent it from being garbage collected. The second to the WeakListener wrapper so it can unregister once registered listener. The second reference is eliminated by using this class. 

Example:
public class Observer {
private AbstractNotifyListener listener = new AbstractNotifyListener() {
public void handle(Bean bean, PropertyReference property) {
// do something
}
};
public void start() {
subject.addChangeListener(property, listener.getWeakListener());
}
public void stop() {
subject.removeChangeListener(property, listener.getWeakListener());
}
}

/**
 * A helper base class for notify listeners. It holds reference to its
 * {@code WeakListener} wrapper.
 * <p>
 * Without this class, an observer which uses weak listeners would need to hold
 * two references. The first to the original {@code ChangeListener} to prevent
 * it from being garbage collected. The second to the {@code WeakListener}
 * wrapper so it can unregister once registered listener. The second reference
 * is eliminated by using this class.
 * <p>
 * Example:
<PRE>
public class Observer {
    private AbstractNotifyListener listener = new AbstractNotifyListener() {
        public void handle(Bean bean, PropertyReference property) {
            // do something
        }
    };

    public void start() {
        subject.addChangeListener(property, listener.getWeakListener());
    }

    public void stop() {
        subject.removeChangeListener(property, listener.getWeakListener());
    }
}
</PRE>
 */
public abstract class AbstractNotifyListener implements InvalidationListener {
    private final WeakInvalidationListener weakListener = new WeakInvalidationListener(this);

    public InvalidationListener getWeakListener() {
        return weakListener;
    }
}