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# Interface java.util.Observer

public interface Observer

A class can implement the `Observer` interface when it wants to be informed of changes in observable objects.

See Also:
  Observable

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update(Observable, Object)
  This method is called whenever the observed object is changed.

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update

     public abstract void update(Observable o,
                                 Object arg)

  This method is called whenever the observed object is changed. An application calls an observable object's `notifyObservers` method to have all the object's observers notified of the change.

  Parameters:
    o - the observable object.
    arg - an argument passed to the `notifyObservers` method.

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