Components added to a container are tracked in a list. The order
of the list will define the components' front-to-back stacking order
within the container. If no index is specified when adding a
component to a container, it will be added to the end of the list
(and hence to the bottom of the stacking order).
Note: For details on the focus subsystem, see
How to Use the Focus Subsystem,
a section in The Java Tutorial, and the
for more information.