Advice on developing my first Java POS application for a small grocery store

[u/Yrpx]

Hi everyone,

I'm a web and mobile development student. I have some programming knowledge, but this is my first time developing a complete application from start to finish.

I've received my first request to build a POS system for a small grocery store, and I'd like to do a good job while also learning from the experience.

The store has only one cashier, so the application should be simple and practical.

The main requirements are:

- Register products by scanning their barcodes and entering their names, prices, and quantities.

- Scan products during checkout and automatically display their names and prices.

- Calculate the total and save each sale.

- Automatically update stock quantities after each sale.

- Review previous sales and check current inventory.

I'd prefer a desktop application that works offline on a single computer.

I'd like to use Java and a database, including SQL if needed, since these are among the technologies I've studied and want to apply in a real project.

I'd appreciate your advice on the following:

1. Is there an existing free and open-source Java POS application that would be suitable for a small grocery store? I'd like to study its code, understand how it works, and modify it to meet the requirements.

2. If such a project exists, which ones would you recommend, preferably projects that are reasonably well-organized, functional, and easy to modify?

3. If modifying an existing project isn't a good option, would building the application from scratch be better?

4. If I build it from scratch, what technologies would you recommend for the user interface and database?

5. Could you suggest a step-by-step development roadmap suitable for someone who knows programming basics but hasn't built a complete application before?

Since this is my first client project, I want to choose a sensible approach rather than waste time on an unsuitable codebase. My goal is to deliver a working application while understanding the code and learning how to develop a complete software project.

I'd appreciate any practical advice, project recommendations, or lessons from your experience. Thank you!

[u/lucashub_dev]

For a small single-cashier POS I'd build it from scratch rather than try to modify an existing codebase, since reading and changing someone else's full project will cost more time than writing the four screens you actually need. For a desktop app that must work offline, Java Swing is the simplest honest choice and keeps you on the Java/SQL stack you want to practice; pair it with an embedded database like H2 or SQLite so there is no server to install and the store keeps working when the Wi-Fi drops. Start by shipping a minimal loop that can register a product by barcode, scan it at checkout to show the price, total a sale, decrement stock, and show yesterday's sales - get that correct before touching receipts, taxes, or a payment integration. Keep the UI and the database access behind small interfaces so you can swap SQLite for MySQL later, and back up the database file every night before you add networking.

[u/Yrpx → u/lucashub_dev]

Thanks for the detailed advice... I'm still learning Java and SQL so I was considering modifying an existing project to understand how everything works before building something myself. But your point about keeping the scope small makes sense. I'll focus on getting the core features working first before adding anything extra... I appreciate the guidance.