In my assignment I've got the following requirement (see below) and I don't think using the NullLayout meets this requirement, plus it doesn't take a genius to notice code that has been generated which would be an instant failure.
Your user interface should be designed with the expectation of future functionality enhancements, and it should establish a framework that will support this with minimal disruption to the users when this occurs.
If I were you, I would avoid using GridBag. The code of the gridbag layout manager is the hardest to read and maintain. If you MUST use gridbag, make sure you understand and document all of the code otherwise you are likely to lose points here.
I'd recommend that you read up on FlowLayout, BorderLayout and BoxLayout. You can build just about anything by combining these layout managers.