It is very common that GUI applications have some menus such
as "File" and "Edit". And usually,"Edit" menu includes such
menu items as "Undo","Cut","Copy","Paste" and so on.
I want to write a GUI application using Java 1.0.2. However,
I don't know clearly how to implement the edit menu,esp. how
to implement that undo function. Making a copy of the edited
text or what?