stdlib

Class Subscriptions<T,U>

java.lang.Object

stdlib.Subscriptions<T,U>

Type Parameters:

T - the type of the publisher

U - the type of the optional data argument

public final class Subscriptions<T,U>
extends java.lang.Object

A helper class which can be used to manage an object's subscriptions.

See Also:

Subscriber

Field Summary

Fields

Modifier and Type	Field and Description
private boolean	changed
private T	publisher
private java.util.List<Subscriber<T,U>>	subscribers

Constructor Summary

Constructors

Constructor and Description
Subscriptions(T publisher) Initializes a new instance of the Subscriptions class with zero subscribers.

Method Summary

Modifier and Type	Method and Description
void	addSubscriber(Subscriber<T,U> subscriber) Adds an subscriber to the set of subscribers for the publisher object, provided that it is not the same as some subscriber already in the set.
void	clearChanged() Indicates that the publisher object has no longer changed, or that it has already notified all of its subscribers of its most recent change, so that hasChanged() will now return false.
int	countSubscribers() Returns the number of subscribers of publisher object.
void	deleteSubscriber(Subscriber<T,U> subscriber) Deletes an subscriber from the set of subscribers.
void	deleteSubscribers() Clears the subscriber list so that the publisher object no longer has any subscribers.
boolean	hasChanged() Returns true if the publisher object has changed; otherwise, false.
void	notifySubscribers() If this object has changed, as indicated by the hasChanged(), then notify all of its subscribers and then clear the changed state.
void	notifySubscribers(U data) If this object has changed, as indicated by the hasChanged(), then notify all of its subscribers and then clear the changed state.
void	setChanged() Flags the publisher object as having changed.

Methods inherited from class java.lang.Object

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

Field Detail

publisher

private final T publisher

subscribers

private final java.util.List<Subscriber<T,U>> subscribers

changed

private boolean changed

Constructor Detail

Subscriptions

public Subscriptions(T publisher)

Initializes a new instance of the Subscriptions class with zero subscribers.

Parameters:

publisher - the object being publisher

Throws:

java.lang.IllegalArgumentException - if publisher is null

Method Detail

addSubscriber

public void addSubscriber(Subscriber<T,U> subscriber)

Adds an subscriber to the set of subscribers for the publisher object, provided that it is not the same as some subscriber already in the set.

Parameters:

subscriber -

Throws:

java.lang.IllegalArgumentException - if the parameter subscriber is null

clearChanged

public void clearChanged()

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

countSubscribers

public int countSubscribers()

Returns the number of subscribers of publisher object.

Returns:

the number of subscribers of publisher object

deleteSubscriber

public void deleteSubscriber(Subscriber<T,U> subscriber)

Deletes an subscriber from the set of subscribers. Passing null to this method will have no effect.

Parameters:

subscriber - the Subscriber to be deleted

deleteSubscribers

public void deleteSubscribers()

Clears the subscriber list so that the publisher object no longer has any subscribers.

hasChanged

public boolean hasChanged()

Returns true if the publisher object has changed; otherwise, false.

Returns:

true if the publisher object has changed; otherwise, false

notifySubscribers

public void notifySubscribers()

If this object has changed, as indicated by the hasChanged(), then notify all of its subscribers and then clear the changed state. This method is equivalent to calling notifySubscribers(null).

notifySubscribers

public void notifySubscribers(U data)

If this object has changed, as indicated by the hasChanged(), then notify all of its subscribers and then clear the changed state.

Parameters:

data - optional event specific data which will be passed to the subscribers

setChanged

public void setChanged()

Flags the publisher object as having changed.