Thread: Super Market Application

I have learned the basic of threading through various resources and now I want to implement a basic supermarket application. The features which I am looking in that application are :-

1. Billing counters where customer will do there checkout.
2. Number of items in each customer's in trolley must be different.
3. To trace weather more checkout are required or not.
4. Calculate billing time, wait time etc.

I am not sure how to start this using thread. If any one can suggest the steps how to proceed with development that will be very helpful. I am planning to use java AWT from UI prospective.

I am planning to implement this using thread only and JavaFX seems good options. But the situation where I am currently stuck is how I cam implement this like what needs to be done first. If any sequence of task are known to me i can start developing those.

Currently from thread coding point of view I am not sure how to start this. If some one any suggest any border idea about this, I am sure i can code it. The UI is not major concern for me but the thing which is creating trouble for me is how to implement functionality,

I hop you have got my concern.

Yes Thanks for suggestion.