Bar Simulator in Java

hi all,
Can any 1 please help me with this thing. i need to create a bar simulator in java,
in the bar there will be four person:
The customer,Barmaid,Land-load and an assistant.
Barmaid and land-load serves the customer,

They need cups,Glass to make drinks for the customer,
if cups or glass not available Assistant replace them,

and customer needs to sit if there is a seat available at the table. of not he waits.
when the customer left the bar, assistant cleans the tables.
thank you,