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 * Copyright (c) 1996, 2008, 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.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package java.awt.event;

import java.awt.Container;

import java.awt.Component;

/**

 * A low-level event which indicates that a container's contents

 * changed because a component was added or removed.

 * <P>

 * Container events are provided for notification purposes ONLY;

 * The AWT will automatically handle changes to the containers

 * contents internally so that the program works properly regardless of

 * whether the program is receiving these events or not.

 * <P>

 * This low-level event is generated by a container object (such as a

 * Panel) when a component is added to it or removed from it.

 * The event is passed to every <code>ContainerListener</code>

 * or <code>ContainerAdapter</code> object which registered to receive such

 * events using the component's <code>addContainerListener</code> method.

 * (<code>ContainerAdapter</code> objects implement the

 * <code>ContainerListener</code> interface.) Each such listener object

 * gets this <code>ContainerEvent</code> when the event occurs.

 * <p>

 * An unspecified behavior will be caused if the {@code id} parameter

 * of any particular {@code ContainerEvent} instance is not

 * in the range from {@code CONTAINER_FIRST} to {@code CONTAINER_LAST}.

 *

 * @see ContainerAdapter

 * @see ContainerListener

 * @see <a href="http://java.sun.com/docs/books/tutorial/post1.0/ui/containerlistener.html">Tutorial: Writing a Container Listener</a>

 *

 * @author Tim Prinzing

 * @author Amy Fowler

 * @since 1.1

 */

public class ContainerEvent extends ComponentEvent {

    /**

     * The first number in the range of ids used for container events.

     */

    public static final int CONTAINER_FIRST             = 300;

    /**

     * The last number in the range of ids used for container events.

     */

    public static final int CONTAINER_LAST              = 301;

   /**

     * This event indicates that a component was added to the container.

     */

    public static final int COMPONENT_ADDED     = CONTAINER_FIRST;

    /**

     * This event indicates that a component was removed from the container.

     */

    public static final int COMPONENT_REMOVED = 1 + CONTAINER_FIRST;

    /**

     * The non-null component that is being added or

     * removed from the Container.

     *

     * @serial

     * @see #getChild()

     */

    Component child;

    /*

     * JDK 1.1 serialVersionUID

     */

    private static final long serialVersionUID = -4114942250539772041L;

    /**

     * Constructs a <code>ContainerEvent</code> object.

     * <p> This method throws an

     * <code>IllegalArgumentException</code> if <code>source</code>

     * is <code>null</code>.

     *

     * @param source The <code>Component</code> object (container)

     *               that originated the event

     * @param id     An integer indicating the type of event.

     *                     For information on allowable values, see

     *                     the class description for {@link ContainerEvent}

     * @param child  the component that was added or removed

     * @throws IllegalArgumentException if <code>source</code> is null

     * @see #getContainer()

     * @see #getID()

     * @see #getChild()

     */

    public ContainerEvent(Component source, int id, Component child) {

        super(source, id);

        this.child = child;

    }

    /**

     * Returns the originator of the event.

     *

     * @return the <code>Container</code> object that originated

     * the event, or <code>null</code> if the object is not a

     * <code>Container</code>.

     */

    public Container getContainer() {

        return (source instanceof Container) ? (Container)source : null;

    }

    /**

     * Returns the component that was affected by the event.

     *

     * @return the Component object that was added or removed

     */

    public Component getChild() {

        return child;

    }

    /**

     * Returns a parameter string identifying this event.

     * This method is useful for event-logging and for debugging.

     *

     * @return a string identifying the event and its attributes

     */

    public String paramString() {

        String typeStr;

        switch(id) {

          case COMPONENT_ADDED:

              typeStr = "COMPONENT_ADDED";

              break;

          case COMPONENT_REMOVED:

              typeStr = "COMPONENT_REMOVED";

              break;

          default:

              typeStr = "unknown type";

        }

        return typeStr + ",child="+child.getName();

    }

}