/* * Copyright (c) 1994, 1998, 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 * or visit www.oracle.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);}