Java SE (Java Platform, Standard Edition)

I am new and useless to programing Java GUIs. I am working on a small (uni/school) project and thought it would add to the app if the program had a GUI.
My goal is to plot out a bunch of 'router'/circles and allow the user to drag them to where they desire them to be.

Since I have no experience with GUIs I do not know where to start.
I have made a little class that extends JFrame and set the layout to null, and plots buttons around the screen that I can interact with. But this is hardly what I want.

Is there some way I can replace these buttons with circles that act the same?
What layout should I be looking into... or should I be looking in a completely different direction.

Any help is appreciated.
Thanks.

M@