| /* java.util.Observable |
| Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. |
| |
| As a special exception, if you link this library with other files to |
| produce an executable, this library does not by itself cause the |
| resulting executable to be covered by the GNU General Public License. |
| This exception does not however invalidate any other reasons why the |
| executable file might be covered by the GNU General Public License. */ |
| |
| |
| package java.util; |
| |
| /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3 |
| * "The Java Language Specification", ISBN 0-201-63451-1 |
| * plus online API docs for JDK 1.2 beta from http://www.javasoft.com. |
| * Status: Believed complete and correct. |
| */ |
| |
| /** |
| * @author Warren Levy <warrenl@cygnus.com> |
| * @date September 2, 1998. |
| */ |
| public class Observable |
| { |
| /** tracks whether this object has changed */ |
| private boolean changed; |
| |
| /* list of the Observers registered as interested in this Observable */ |
| private Vector observers; |
| |
| /* TBD: This might be better implemented as an Observer[] |
| * but that would mean writing more code rather than making use of |
| * the existing Vector class (this also implies a larger text code |
| * space in resulting executables). The tradeoff is one of speed |
| * (manipulating the Observer[] directly) vs. size/reuse. In the future, |
| * we may decide to make the tradeoff and reimplement with an Observer[]. |
| */ |
| |
| /** |
| * Constructs an Observable with zero Observers. |
| */ |
| public Observable() |
| { |
| changed = false; |
| observers = new Vector(); |
| } |
| |
| /** |
| * Adds an Observer. If the observer was already added this method does |
| * nothing. |
| * |
| * @param observer Observer to add. |
| */ |
| public synchronized void addObserver(Observer observer) |
| { |
| if (!observers.contains(observer)) |
| observers.addElement(observer); |
| } |
| |
| /** |
| * Reset this Observable's state to unchanged. |
| */ |
| protected synchronized void clearChanged() |
| { |
| changed = false; |
| } |
| |
| /** |
| * @return Number of Observers for this Observable. |
| */ |
| public synchronized int countObservers() |
| { |
| return observers.size(); |
| } |
| |
| /** |
| * Deletes an Observer of this Observable. |
| * |
| * @param victim Observer to delete. |
| */ |
| public synchronized void deleteObserver(Observer victim) |
| { |
| observers.removeElement(victim); |
| } |
| |
| /** |
| * Deletes all Observers of this Observable. |
| */ |
| public synchronized void deleteObservers() |
| { |
| observers.removeAllElements(); |
| } |
| |
| /** |
| * @return Whether or not this Observable has changed. |
| */ |
| public synchronized boolean hasChanged() |
| { |
| return changed; |
| } |
| |
| /** |
| * If the Observable has actually changed then tell all Observers about it, |
| * then resets state to unchanged. |
| */ |
| public void notifyObservers() |
| { |
| notifyObservers(null); |
| } |
| |
| /** |
| * If the Observable has actually changed then tell all Observers about it, |
| * then resets state to unchanged. |
| * Note that though the order of notification is unspecified in subclasses, |
| * in Observable it is in the order of registration. |
| * |
| * @param obj Arguement to Observer's update method. |
| */ |
| public void notifyObservers(Object obj) |
| { |
| if (!hasChanged()) |
| return; |
| Vector ob1 = (Vector) observers.clone(); |
| |
| for (int i = 0; i < ob1.size(); i++) |
| ((Observer) ob1.elementAt(i)).update(this, obj); |
| |
| clearChanged(); |
| } |
| |
| /** |
| * Marks this Observable as having changed. |
| */ |
| protected synchronized void setChanged() |
| { |
| changed = true; |
| } |
| } |