java.util
Class Observable

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

public class Observable

extends Object

Untamed:

Field Summary

private boolean	changed
private Vector	obs

Constructor Summary

Observable()
Enabled: Construct an Observable with zero Observers.

Method Summary

void	addObserver(Observer o) Enabled: Adds an observer to the set of observers for this object, provided that it is not the same as some observer already in the set.
protected void	clearChanged() Indicates that this object has no longer changed, or that it has already notified all of its observers of its most recent change, so that the hasChanged method will now return false.
int	countObservers() Enabled: Returns the number of observers of this Observable object.
void	deleteObserver(Observer o) Enabled: Deletes an observer from the set of observers of this object.
void	deleteObservers() Enabled: Clears the observer list so that this object no longer has any observers.
boolean	hasChanged() Enabled: Tests if this object has changed.
void	notifyObservers() Enabled: If this object has changed, as indicated by the hasChanged method, then notify all of its observers and then call the clearChanged method to indicate that this object has no longer changed.
void	notifyObservers(Object arg) Enabled: If this object has changed, as indicated by the hasChanged method, then notify all of its observers and then call the clearChanged method to indicate that this object has no longer changed.
protected void	setChanged() Marks this Observable object as having been changed; the hasChanged method will now return true.

Methods inherited from class java.lang.Object

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

Field Detail

changed

private boolean changed

obs

private Vector obs

Constructor Detail

Observable

public Observable()

Enabled: Construct an Observable with zero Observers.

Method Detail

addObserver

public void addObserver(Observer o)

Enabled: Adds an observer to the set of observers for this object, provided that it is not the same as some observer already in the set. The order in which notifications will be delivered to multiple observers is not specified. See the class comment.

Parameters:

o - an observer to be added.

Throws:

NullPointerException - if the parameter o is null.

deleteObserver

public void deleteObserver(Observer o)

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

Parameters:

o - the observer to be deleted.

notifyObservers

public void notifyObservers()

Enabled: If this object has changed, as indicated by the hasChanged method, then notify all of its observers and then call the clearChanged method to indicate that this object has no longer changed.

Each observer has its update method called with two arguments: this observable object and null. In other words, this method is equivalent to:

notifyObservers(null)

See Also:

java.util.Observable#clearChanged(), java.util.Observable#hasChanged(), java.util.Observer#update(java.util.Observable, java.lang.Object)

notifyObservers

public void notifyObservers(Object arg)

Enabled: If this object has changed, as indicated by the hasChanged method, then notify all of its observers and then call the clearChanged method to indicate that this object has no longer changed.

Each observer has its update method called with two arguments: this observable object and the arg argument.

Parameters:

arg - any object.

See Also:

java.util.Observable#clearChanged(), java.util.Observable#hasChanged(), java.util.Observer#update(java.util.Observable, java.lang.Object)

deleteObservers

public void deleteObservers()

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

setChanged

protected void setChanged()

Marks this Observable object as having been changed; the hasChanged method will now return true.

clearChanged

protected void clearChanged()

Indicates that this object has no longer changed, or that it has already notified all of its observers of its most recent change, so that the hasChanged method will now return false. This method is called automatically by the notifyObservers methods.

See Also:

java.util.Observable#notifyObservers(), java.util.Observable#notifyObservers(java.lang.Object)

hasChanged

public boolean hasChanged()

Enabled: Tests if this object has changed.

Returns:

true if and only if the setChanged method has been called more recently than the clearChanged method on this object; false otherwise.

See Also:

java.util.Observable#clearChanged(), java.util.Observable#setChanged()

countObservers

public int countObservers()

Enabled: Returns the number of observers of this Observable object.

Returns:

the number of observers of this object.