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 6 * under the terms of the GNU General Public License version 2 only, as 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 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package 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 */ 35 public 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 */ update(Observable o, Object arg)46 void update(Observable o, Object arg); 47 } 48