thank you for your reply.
in fact I'm designing an application program that has many linked
frames and i wanted to make it look more professional by using full
screen mode .
so I need main frame that contains menus and buttoons which make the
other frames to appear(not over the whole screen).
I tried to do so using JFrame but they seem to appear in the back of
my full screen frame and i want them in front of it.
I think internal frame will solve this, thanks