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25 package java.util;
26 
27 /**
28  * A class can implement the {@code Observer} interface when it
29  * wants to be informed of changes in observable objects.
30  *
31  * @author  Chris Warth
32  * @see     java.util.Observable
33  * @since   1.0
34  *
35  * @deprecated
36  * This interface has been deprecated. See the {@link Observable}
37  * class for further information.
38  */
39 @Deprecated(since="9")
40 public interface Observer {
41     /**
42      * This method is called whenever the observed object is changed. An
43      * application calls an {@code Observable} object's
44      * {@code notifyObservers} method to have all the object's
45      * observers notified of the change.
46      *
47      * @param   o     the observable object.
48      * @param   arg   an argument passed to the {@code notifyObservers}
49      *                 method.
50      */
update(Observable o, Object arg)51     void update(Observable o, Object arg);
52 }
53