001/* Observer.java -- an object that will be informed of changes in an Observable 002 Copyright (C) 1998, 1999, 2001, 2002, 2005 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package java.util; 040 041/** 042 * Interface that is implemented when a class wants to be informed of changes 043 * in Observable objects. 044 * 045 * @author Warren Levy (warrenl@cygnus.com) 046 * @see Observable 047 * @status updated to 1.4 048 */ 049public interface Observer 050{ 051 /** 052 * This method is called whenever the observable object changes, and has 053 * called <code>notifyObservers</code>. The Observable object can pass 054 * arbitrary information in the second parameter. 055 * 056 * @param observable the Observable object that changed 057 * @param arg arbitrary information, usually relating to the change 058 */ 059 void update(Observable observable, Object arg); 060}