java.util
Class Observable

java.lang.Object
  |
  +--java.util.Observable

public class Observable

extends Object

This class should be subclassed by observable object, or "data" in the Model-View paradigm. An Observable object may have any number of Observers. Whenever the Observable instance changes, it notifies all of its observers. Notification is done by calling the update() method on all observers.

Constructor Summary

Observable()

Method Summary

void	addObserver(Observer o) Adds an observer to the observer list.
protected void	clearChanged() Clears an observable change.
int	countObservers() Counts the number of observers.
void	deleteObserver(Observer o) Deletes an observer from the observer list.
void	deleteObservers() Deletes observers from the observer list.
boolean	hasChanged() Returns a true boolean if an observable change has occurred.
void	notifyObservers() Notifies all observers if an observable change occurs.
void	notifyObservers(Object arg) Notifies all observers of the specified observable change which occurred.
protected void	setChanged() Sets a flag to note an observable change.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Observable

public Observable()

Method Detail

addObserver

public void addObserver(Observer o)

Adds an observer to the observer list.

Parameters:

o - the observer to be added

deleteObserver

public void deleteObserver(Observer o)

Deletes an observer from the observer list.

Parameters:

o - the observer to be deleted

notifyObservers

public void notifyObservers()

Notifies all observers if an observable change occurs.

notifyObservers

public void notifyObservers(Object arg)

Notifies all observers of the specified observable change which occurred.

Parameters:

arg - what is being notified

deleteObservers

public void deleteObservers()

Deletes observers from the observer list.

setChanged

protected void setChanged()

Sets a flag to note an observable change.

clearChanged

protected void clearChanged()

Clears an observable change.

hasChanged

public boolean hasChanged()

Returns a true boolean if an observable change has occurred.

countObservers

public int countObservers()

Counts the number of observers.