posted 8 years ago
The best way to get this understanding on your own (because you surely will have more questions as you study more), is to refer to the API. If you look up JFrame.getContentPane on the API, you'll see that it returns a Container. If you hypertext link over to Container, you'll see that it has an add method. Using the API is like exercising a muscle. The more you do it, the better you get at it. Good luck.