THE PACKAGE JAVA.UTIL

java.util.Observer

21.8

21.8 The Interface

java.util.Observer

A class should implement the

Observer

 interface if it is to be notified whenever

an

Observable

 object has been changed. See the

Observable

 class ( 21.7) for a

discussion of how

Observer

 objects are notified.

public interface Observer {

public void update(Observable o, Object arg);

}

21.8.1

public void update(Observable o, Object arg)

When an

Observable

 object has been changed and its

notifyObservers

method ( 21.7.6) is called, every

Observer

 object in its set of

observers

 is noti 

fied by invoking its

update

 method, passing it two arguments: the

Observable

object and another argument specified by the call to the

notifyObservers

method.

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