src/java.desktop/share/classes/javax/swing/DefaultSingleSelectionModel.java

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 * 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 javax.swing;

import javax.swing.event.*;
import java.io.Serializable;
import java.util.EventListener;

/**
 * A generic implementation of SingleSelectionModel.
 * <p>
 * <strong>Warning:</strong>
 * Serialized objects of this class will not be compatible with
 * future Swing releases. The current serialization support is
 * appropriate for short term storage or RMI between applications running
 * the same version of Swing.  As of 1.4, support for long term storage
 * of all JavaBeans
 * has been added to the <code>java.beans</code> package.
 * Please see {@link java.beans.XMLEncoder}.
 *
 * @author Dave Moore
 * @since 1.2
 */
@SuppressWarnings("serial") // Same-version serialization only
public class DefaultSingleSelectionModel implements SingleSelectionModel,
Serializable {
    /**
     * Only one ModelChangeEvent is needed per model instance since the
     * event's only (read-only) state is the source property.  The source
     * of events generated here is always "this".
     */
    protected transient ChangeEvent changeEvent = null;
    /** The collection of registered listeners */
    protected EventListenerList listenerList = new EventListenerList();

    private int index = -1;

    /**
     * Constructs a {@code DefaultSingleSelectionModel}.
     */
    public DefaultSingleSelectionModel() {}

    /**
     * {@inheritDoc}
     */
    public int getSelectedIndex() {
        return index;
    }

    /**
     * {@inheritDoc}
     */
    public void setSelectedIndex(int index) {
        if (this.index != index) {
            this.index = index;
            fireStateChanged();
        }
    }

    /**
     * {@inheritDoc}
     */
    public void clearSelection() {
        setSelectedIndex(-1);
    }

    /**
     * {@inheritDoc}
     */
    public boolean isSelected() {
        boolean ret = false;
        if (getSelectedIndex() != -1) {
            ret = true;
        }
        return ret;
    }

    /**
     * Adds a <code>ChangeListener</code> to the button.
     */
    public void addChangeListener(ChangeListener l) {
        listenerList.add(ChangeListener.class, l);
    }

    /**
     * Removes a <code>ChangeListener</code> from the button.
     */
    public void removeChangeListener(ChangeListener l) {
        listenerList.remove(ChangeListener.class, l);
    }

    /**
     * Returns an array of all the change listeners
     * registered on this <code>DefaultSingleSelectionModel</code>.
     *
     * @return all of this model's <code>ChangeListener</code>s
     *         or an empty
     *         array if no change listeners are currently registered
     *
     * @see #addChangeListener
     * @see #removeChangeListener
     *
     * @since 1.4
     */
    public ChangeListener[] getChangeListeners() {
        return listenerList.getListeners(ChangeListener.class);
    }

    /**
     * Notifies all listeners that have registered interest for
     * notification on this event type.  The event instance
     * is created lazily.
     * @see EventListenerList
     */
    protected void fireStateChanged() {
        // Guaranteed to return a non-null array
        Object[] listeners = listenerList.getListenerList();
        // Process the listeners last to first, notifying
        // those that are interested in this event
        for (int i = listeners.length-2; i>=0; i-=2) {
            if (listeners[i]==ChangeListener.class) {
                // Lazily create the event:
                if (changeEvent == null)
                    changeEvent = new ChangeEvent(this);
                ((ChangeListener)listeners[i+1]).stateChanged(changeEvent);
            }
        }
    }

    /**
     * Returns an array of all the objects currently registered as
     * <code><em>Foo</em>Listener</code>s
     * upon this model.
     * <code><em>Foo</em>Listener</code>s
     * are registered using the <code>add<em>Foo</em>Listener</code> method.
     * <p>
     * You can specify the <code>listenerType</code> argument
     * with a class literal, such as <code><em>Foo</em>Listener.class</code>.
     * For example, you can query a <code>DefaultSingleSelectionModel</code>
     * instance <code>m</code>
     * for its change listeners
     * with the following code:
     *
     * <pre>ChangeListener[] cls = (ChangeListener[])(m.getListeners(ChangeListener.class));</pre>
     *
     * If no such listeners exist,
     * this method returns an empty array.
     *
     * @param <T>  the type of {@code EventListener} class being requested
     * @param listenerType  the type of listeners requested;
     *          this parameter should specify an interface
     *          that descends from <code>java.util.EventListener</code>
     * @return an array of all objects registered as
     *          <code><em>Foo</em>Listener</code>s
     *          on this model,
     *          or an empty array if no such
     *          listeners have been added
     * @throws ClassCastException if <code>listenerType</code> doesn't
     *          specify a class or interface that implements
     *          <code>java.util.EventListener</code>
     *
     * @see #getChangeListeners
     *
     * @since 1.3
     */
    public <T extends EventListener> T[] getListeners(Class<T> listenerType) {
        return listenerList.getListeners(listenerType);
    }
}