/*

 * Copyright 1994-1998 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

 * have any questions.

 */

package java.util;

/**

 * A class can implement the <code>Observer</code> interface when it

 * wants to be informed of changes in observable objects.

 *

 * @author  Chris Warth

 * @see     java.util.Observable

 * @since   JDK1.0

 */

public interface Observer {

    /**

     * This method is called whenever the observed object is changed. An

     * application calls an <tt>Observable</tt> object's

     * <code>notifyObservers</code> method to have all the object's

     * observers notified of the change.

     *

     * @param   o     the observable object.

     * @param   arg   an argument passed to the <code>notifyObservers</code>

     *                 method.

     */

    void update(Observable o, Object arg);

}