Many listener interfaces define several methods that may not be required by your application. However, whenever you implement an interface you must provide the implementation for all its methods (refer to Chapter 6). The designers of the Swing APIs came up with the idea of Adapter classes for event processing, which save you the trouble of implementing the various interface methods. A typical Adapter class implements a certain listener interface and provides empty implementation to all its methods. You simply need to extend your class from the Adapter class and override the desired methods to achieve whatever application functionality your application needs.
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