A GUI component constructed from a container class is expected to contain other GUI components.
Objects of the
or of classes based on
have common characteristics.
They can contain components,
they themselves can be placed inside containers, they can be displayed
on the monitor,
they generate events,
they register event listeners,
and so on.
Since all Swing classes have
as an ancestor, all Swing objects have these characteristics.
There are more Swing classes than those shown.
For example there are several button types derived from