The listener interface for receiving item events.
The class that is interested in processing an item event
implements this interface. The object created with that
class is then registered with a component using the
component's
addItemListener method. When an
item-selection event occurs, the listener object's
itemStateChanged method is invoked.
Invoked when an item has been selected or deselected by the user.
The code written for this method performs the operations
that need to occur when an item is selected (or deselected).