de.mhus.lib.core.util

Class WeakObservable

java.lang.Object

java.util.Observable

de.mhus.lib.core.util.WeakObservable

public class WeakObservable
extends Observable

Constructor Summary

Constructors

Constructor and Description
WeakObservable()

Method Summary

Methods

Modifier and Type	Method and Description
void	addObserver(Observer o) 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() Returns the number of observers of this Observable object.
void	deleteObserver(Observer o) Deletes an observer from the set of observers of this object.
void	deleteObservers() Clears the observer list so that this object no longer has any observers.
boolean	hasChanged() Tests if this object has changed.
void	notifyObservers() 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) 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	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

Constructor Detail

WeakObservable

public WeakObservable()

Method Detail

addObserver

public void addObserver(Observer o)

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.

Overrides:

addObserver in class Observable

Parameters:

o - an observer to be added.

Throws:

NullPointerException - if the parameter o is null.

deleteObserver

public void deleteObserver(Observer o)

Deletes an observer from the set of observers of this object. Passing null to this method will have no effect.

Overrides:

deleteObserver in class Observable

Parameters:

o - the observer to be deleted.

notifyObservers

public void notifyObservers()

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)

Overrides:

notifyObservers in class Observable

See Also:

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

notifyObservers

public void notifyObservers(Object arg)

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.

Overrides:

notifyObservers in class Observable

Parameters:

arg - any object.

See Also:

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

deleteObservers

public void deleteObservers()

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

Overrides:

deleteObservers in class Observable

setChanged

public void setChanged()

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

Overrides:

setChanged in class Observable

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.

Overrides:

clearChanged in class Observable

See Also:

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

hasChanged

public boolean hasChanged()

Tests if this object has changed.

Overrides:

hasChanged in class Observable

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:

Observable.clearChanged(), Observable.setChanged()

countObservers

public int countObservers()

Returns the number of observers of this Observable object.

Overrides:

countObservers in class Observable

Returns:

the number of observers of this object.