Many event-listener interfaces, such as MouseListener
and MouseMotionListener
, contain multiple methods. It’s not always desirable to declare every method in an event-listener interface. For instance, an app may need only the mouseClicked
handler from MouseListener
or the mouseDragged
handler from MouseMotionListener
. Interface WindowListener
specifies seven window event-handling methods. For many of the listener interfaces that have multiple methods, packages java.awt.event
and javax.swing.event
provide event-listener adapter classes. An adapter class implements an interface and provides a default implementation (with an empty method body) of each method in the interface. You can extend an adapter class to inherit the default implementation of every method and subsequently override only the method(s) you need for event handling.