Coolest Mini projects suggestion please

Question

Suppose you've created some Java programs from basic to intermediate lvl, now looking to build some mini projects like fully functional calculator to show it in your portfolios for jobs
What would be some interesting ideas to pick?

Answer 1

supermarket manager or something that depends on DATABASES

Answer 2

Airline reservation system?

Answer 3

Thank u
ABADA S
Sonic
Airline reservations system , do I need to know JavaScript (if its gonna open in a browser) in order to do this or it can be done with GUI in Java only