public interface WindowFocusListener extends EventListener
WindowEvents, including
 WINDOW_GAINED_FOCUS and WINDOW_LOST_FOCUS events.
 The class that is interested in processing a WindowEvent
 either implements this interface (and
 all the methods it contains) or extends the abstract
 WindowAdapter class (overriding only the methods of interest).
 The listener object created from that class is then registered with a
 Window
 using the Window's addWindowFocusListener method.
 When the Window's
 status changes by virtue of it being opened, closed, activated, deactivated,
 iconified, or deiconified, or by focus being transfered into or out of the
 Window, the relevant method in the listener object is invoked,
 and the WindowEvent is passed to it.WindowAdapter, 
WindowEvent, 
Tutorial: Writing a Window Listener| Modifier and Type | Method and Description | 
|---|---|
| void | windowGainedFocus(WindowEvent e)Invoked when the Window is set to be the focused Window, which means
 that the Window, or one of its subcomponents, will receive keyboard
 events. | 
| void | windowLostFocus(WindowEvent e)Invoked when the Window is no longer the focused Window, which means
 that keyboard events will no longer be delivered to the Window or any of
 its subcomponents. | 
void windowGainedFocus(WindowEvent e)
void windowLostFocus(WindowEvent e)
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