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package cgeo.geocaching.utils;
/**
* Interface for subjects objects. Those can be observed by objects implementing the {@link IObserver} interface.
*
* @param <T>
* the kind of data to observe
*/
public interface ISubject<T> {
/**
* Add an observer to the observers list.
* <p/>
* Observers will be notified with no particular order.
*
* @param observer
* the observer to add
* @return true if the observer has been added, false if it was present already
*/
public boolean addObserver(final IObserver<? super T> observer);
/**
* Delete an observer from the observers list.
*
* @param observer
* the observer to remove
* @return true if the observer has been removed, false if it was not in the list of observers
*/
public boolean deleteObserver(final IObserver<? super T> observer);
/**
* Number of observers currently observing the object.
*
* @return the number of observers
*/
public int sizeObservers();
/**
* Notify all the observers that new data is available.
* <p/>
* The {@link IObserver#update(Object)} method of each observer will be called with no particular order.
*
* @param data
* the updated data
* @return true if at least one observer was notified, false if there were no observers
*/
public boolean notifyObservers(final T data);
/**
* Clear the observers list.
*
* @return true if there were observers before calling this method, false if the observers list was empty
*/
public boolean clearObservers();
}
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