Observer.java revision 51b1b6997fd3f980076b8081f7f1165ccc2a4008 
1/*
2 * Copyright (c) 1994, 1998, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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24 */
25package java.util;
26
27/**
28 * A class can implement the <code>Observer</code> interface when it
29 * wants to be informed of changes in observable objects.
30 *
31 * @author  Chris Warth
32 * @see     java.util.Observable
33 * @since   JDK1.0
34 */
35public interface Observer {
36    /**
37     * This method is called whenever the observed object is changed. An
38     * application calls an <tt>Observable</tt> object's
39     * <code>notifyObservers</code> method to have all the object's
40     * observers notified of the change.
41     *
42     * @param   o     the observable object.
43     * @param   arg   an argument passed to the <code>notifyObservers</code>
44     *                 method.
45     */
46    void update(Observable o, Object arg);
47}
48