99 lines
2.4 KiB
Java
99 lines
2.4 KiB
Java
/* Copyright (C) 1998, 1999 Cygnus Solutions
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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package java.util;
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/**
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* @author Warren Levy <warrenl@cygnus.com>
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* @date September 2, 1998.
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*/
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/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
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* "The Java Language Specification", ISBN 0-201-63451-1
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* plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
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* Status: Believed complete and correct.
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*/
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public class Observable
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{
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/* tracks whether this object has changed */
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private boolean changed;
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/* list of the Observers registered as interested in this Observable */
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private Vector observerVec;
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/* TBD: This might be better implemented as an Observer[]
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* but that would mean writing more code rather than making use of
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* the existing Vector class (this also implies a larger text code
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* space in resulting executables). The tradeoff is one of speed
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* (manipulating the Observer[] directly) vs. size/reuse. In the future,
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* we may decide to make the tradeoff and reimplement with an Observer[].
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*/
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public Observable()
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{
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changed = false;
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observerVec = new Vector();
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}
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public synchronized void addObserver(Observer obs)
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{
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// JDK 1.2 spec says not to add this if it is already there
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if (!observerVec.contains(obs))
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observerVec.addElement(obs);
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}
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protected synchronized void clearChanged()
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{
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changed = false;
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}
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public synchronized int countObservers()
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{
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return observerVec.size();
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}
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public synchronized void deleteObserver(Observer obs)
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{
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observerVec.removeElement(obs);
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}
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public synchronized void deleteObservers()
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{
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observerVec.removeAllElements();
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}
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public synchronized boolean hasChanged()
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{
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return changed;
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}
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public void notifyObservers()
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{
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notifyObservers(null);
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}
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public void notifyObservers(Object arg)
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{
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if (changed)
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{
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/* The JDK 1.2 spec states that though the order of notification
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* is unspecified in subclasses, in Observable it is in the order
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* of registration.
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*/
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for (int i = 0, numObs = observerVec.size(); i < numObs; i++)
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((Observer) (observerVec.elementAt(i))).update(this, arg);
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changed = false;
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}
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}
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protected synchronized void setChanged()
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{
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changed = true;
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}
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}
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