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Java in a Nutshell

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The java.util Package

30.15 java.util.Observable (JDK 1.0)

This class is the superclass of all "observable" objects to be used in an object-oriented model/view paradigm. The class methods allow you to add and delete Observer objects to and from an Observable's list, and to notify all of the Observer objects on the list. Observer objects are "notified" by invoking their update() method. Observable also maintains an internal "changed" flag, which may be set and cleared by the Observable, and which may be queried with hasChanged() by any interested observer.

public class Observable extends Object {
    // Public Constructor
        1.1public Observable();
    // Public Instance Methods
            public synchronized void addObserver(Observer o);
            public synchronized int countObservers();
            public synchronized void deleteObserver(Observer o);
            public synchronized void deleteObservers();
            public synchronized boolean hasChanged();
            public void notifyObservers();
            public void notifyObservers(Object arg);
    // Protected Instance Methods
            protected synchronized void clearChanged();
            protected synchronized void setChanged();

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