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public interface Observable<E>
Method Summary | |
---|---|
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. |
int |
countObservers()
Returns the number of observers of this BaseObservable 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(E 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. |
Method Detail |
---|
void addObserver(Observer o)
o
- an observer to be added.
java.lang.NullPointerException
- if the parameter o is null.void deleteObserver(Observer o)
null
to this method will have no effect.
o
- the observer to be deleted.void notifyObservers() throws java.lang.Exception
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)
java.lang.Exception
Observable.clearChanged()
,
Observable.hasChanged()
,
Observer.update(java.util.Observable, java.lang.Object)
void notifyObservers(E arg) throws java.lang.Exception
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.
arg
- any object.
java.lang.Exception
Observable.clearChanged()
,
Observable.hasChanged()
,
Observer.update(java.util.Observable, java.lang.Object)
void deleteObservers()
boolean hasChanged()
true
if and only if the setChanged
method has been called more recently than the
clearChanged
method on this object; false
otherwise.Observable.clearChanged()
,
Observable.setChanged()
int countObservers()
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