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

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package javax.swing;

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

/**
 * The abstract definition for the data model that provides
 * a <code>List</code> with its contents.
 * <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}.
 *
 * @param <E> the type of the elements of this model
 *
 * @author Hans Muller
 * @since 1.2
 */
@SuppressWarnings("serial") // Same-version serialization only
public abstract class AbstractListModel<E> implements ListModel<E>, Serializable
{
    /**
     * The listener list.
     */
    protected EventListenerList listenerList = new EventListenerList();

    /**
     * Constructor for subclasses to call.
     */
    protected AbstractListModel() {}

    /**
     * Adds a listener to the list that's notified each time a change
     * to the data model occurs.
     *
     * @param l the <code>ListDataListener</code> to be added
     */
    public void addListDataListener(ListDataListener l) {
        listenerList.add(ListDataListener.class, l);
    }


    /**
     * Removes a listener from the list that's notified each time a
     * change to the data model occurs.
     *
     * @param l the <code>ListDataListener</code> to be removed
     */
    public void removeListDataListener(ListDataListener l) {
        listenerList.remove(ListDataListener.class, l);
    }


    /**
     * Returns an array of all the list data listeners
     * registered on this <code>AbstractListModel</code>.
     *
     * @return all of this model's <code>ListDataListener</code>s,
     *         or an empty array if no list data listeners
     *         are currently registered
     *
     * @see #addListDataListener
     * @see #removeListDataListener
     *
     * @since 1.4
     */
    public ListDataListener[] getListDataListeners() {
        return listenerList.getListeners(ListDataListener.class);
    }


    /**
     * <code>AbstractListModel</code> subclasses must call this method
     * <b>after</b>
     * one or more elements of the list change.  The changed elements
     * are specified by the closed interval index0, index1 -- the endpoints
     * are included.  Note that
     * index0 need not be less than or equal to index1.
     *
     * @param source the <code>ListModel</code> that changed, typically "this"
     * @param index0 one end of the new interval
     * @param index1 the other end of the new interval
     * @see EventListenerList
     * @see DefaultListModel
     */
    protected void fireContentsChanged(Object source, int index0, int index1)
    {
        Object[] listeners = listenerList.getListenerList();
        ListDataEvent e = null;

        for (int i = listeners.length - 2; i >= 0; i -= 2) {
            if (listeners[i] == ListDataListener.class) {
                if (e == null) {
                    e = new ListDataEvent(source, ListDataEvent.CONTENTS_CHANGED, index0, index1);
                }
                ((ListDataListener)listeners[i+1]).contentsChanged(e);
            }
        }
    }


    /**
     * <code>AbstractListModel</code> subclasses must call this method
     * <b>after</b>
     * one or more elements are added to the model.  The new elements
     * are specified by a closed interval index0, index1 -- the endpoints
     * are included.  Note that
     * index0 need not be less than or equal to index1.
     *
     * @param source the <code>ListModel</code> that changed, typically "this"
     * @param index0 one end of the new interval
     * @param index1 the other end of the new interval
     * @see EventListenerList
     * @see DefaultListModel
     */
    protected void fireIntervalAdded(Object source, int index0, int index1)
    {
        Object[] listeners = listenerList.getListenerList();
        ListDataEvent e = null;

        for (int i = listeners.length - 2; i >= 0; i -= 2) {
            if (listeners[i] == ListDataListener.class) {
                if (e == null) {
                    e = new ListDataEvent(source, ListDataEvent.INTERVAL_ADDED, index0, index1);
                }
                ((ListDataListener)listeners[i+1]).intervalAdded(e);
            }
        }
    }


    /**
     * <code>AbstractListModel</code> subclasses must call this method
     * <b>after</b> one or more elements are removed from the model.
     * <code>index0</code> and <code>index1</code> are the end points
     * of the interval that's been removed.  Note that <code>index0</code>
     * need not be less than or equal to <code>index1</code>.
     *
     * @param source the <code>ListModel</code> that changed, typically "this"
     * @param index0 one end of the removed interval,
     *               including <code>index0</code>
     * @param index1 the other end of the removed interval,
     *               including <code>index1</code>
     * @see EventListenerList
     * @see DefaultListModel
     */
    protected void fireIntervalRemoved(Object source, int index0, int index1)
    {
        Object[] listeners = listenerList.getListenerList();
        ListDataEvent e = null;

        for (int i = listeners.length - 2; i >= 0; i -= 2) {
            if (listeners[i] == ListDataListener.class) {
                if (e == null) {
                    e = new ListDataEvent(source, ListDataEvent.INTERVAL_REMOVED, index0, index1);
                }
                ((ListDataListener)listeners[i+1]).intervalRemoved(e);
            }
        }
    }

    /**
     * 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 list model
     * <code>m</code>
     * for its list data listeners
     * with the following code:
     *
     * <pre>ListDataListener[] ldls = (ListDataListener[])(m.getListeners(ListDataListener.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 #getListDataListeners
     *
     * @since 1.3
     */
    public <T extends EventListener> T[] getListeners(Class<T> listenerType) {
        return listenerList.getListeners(listenerType);
    }
}