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package cgeo.geocaching.utils;
/**
* Synchronized implementation of the {@link ISubject} interface with an added pull interface.
*
* @param <T>
* the kind of data to observe
*/
public class MemorySubject<T> extends Subject<T> {
/**
* The latest version of the observed data.
* <p/>
* A child class implementation may want to set this field from its constructors, in case early observers request
* the data before it got a chance to get updated. Otherwise, <code>null</code> will be returned until updated
* data is available.
*/
private T memory;
@Override
public synchronized boolean addObserver(final IObserver<? super T> observer) {
final boolean added = super.addObserver(observer);
if (added && memory != null) {
observer.update(memory);
}
return added;
}
@Override
public synchronized boolean notifyObservers(final T data) {
memory = data;
return super.notifyObservers(data);
}
/**
* Get the memorized version of the data.
*
* @return the initial data set by the subject (which may be <code>null</code>),
* or the updated data if it is available
*/
public synchronized T getMemory() {
return memory;
}
}
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