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public  class  java.util.Observable
    extends  java.lang.Object  (I-§1.12)
{
        // Constructors
    public Observable();	§3.5.1

        // Methods
    public void addObserver(Observer  o);	§3.5.2
    protected void clearChanged();	§3.5.3
    public int countObservers();	§3.5.4
    public void deleteObserver(Observer  o);	§3.5.5
    public void deleteObservers();	§3.5.6
    public boolean hasChanged();	§3.5.7
    public void notifyObservers();	§3.5.8
    public void notifyObservers(Object  arg);	§3.5.9
    protected void setChanged();	§3.5.10
}

An observable object can have one or more observers (I-§3.12). After an observerable instance changes, an application calling the Observerable's notifyObservers method (§3.5.8, §3.5.9) causes all of its observers to be notified of the change by a call to their update method (I-§3.12.1).

The default constructor.

Adds an observer to the set of observers for this object.

Parameters:

o - an observer to be added

Indicates that this object has no longer changed, or that it has already notified all of its observers of its most recent change. This method is call automatically by the notifyObservers methods (§3.5.8, §3.5.9).

Returns:

the number of observers of this object.

Deletes an observer from the set of observers of this object.

Parameters:

o - the observer to be deleted

Clears the observer list so that this object no longer has any observers.

Determines if this object has changed.

Returns:

true if the setChanged method (I-§3.5.10) has been called more recently than the clearChanged (I-§3.5.3) method on this object; false otherwise.

If this object has changed, as indicated by the hasChanged method (I-§3.5.7), then notify all of its observers and then call the clear-Changed method (I-§3.5.3) to indicate that this object has no longer changed.

Each observer has its update method (I-§3.12.1) called with two arguments: the observable object and null.

If this object has changed, as indicated by the hasChanged method (I-§3.5.7), then notify all of its observers and then call the clearChanged method (I-§3.5.3) to indicate that this object has no longer changed.

Each observer has its update method (I-§3.12.1) called with two arguments: the observable object and the arg argument.

Parameters:

arg - any object.

Indicates that this object has changed.

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