The Dummy Frame
If a root component in your hierarchy is not a
Frame, Dialog, FileDialog,
Window, JFrame, JDialog or JWindow,
then a Dummy Frame or Dummy JFrame (depending on whether
the component is a Swing component or not) is created as a
substitute to display your design. This is useful if you want
to create a method which creates a component or group of
components - for example, a group of labels and text fields
which you wish to use again and again in your application, or
you may have a Choice component which you have loaded
with a list of color names which you wish to use in multiple
dialogs; making the Choice a hierarchy on its own would allow
you to do this.