HierarchyBoundsAdapter class (overriding only the method of
interest).
The listener object created from that class is then registered with a
Component using the Component's addHierarchyBoundsListener
method. When the hierarchy to which the Component belongs changes by
the resizing or movement of an ancestor, the relevant method in the listener
object is invoked, and the HierarchyEvent is passed to it.
Hierarchy events are provided for notification purposes ONLY;
The AWT will automatically handle changes to the hierarchy internally so
that GUI layout works properly regardless of whether a
program registers an HierarchyBoundsListener or not.