📎 This article includes 1 downloadable practice file ↓
📘 Java Beginner Course · Lesson 8 of 8
In this article Extend it Next steps Practice The project file builds an invoice for Iyer Stores, groups amounts by item with a TreeMap, calculates GST at 18% and prints taxable, GST and total.
Extend it
CGST/SGST vs IGST based on state codes.
Read lines from a CSV file (Lesson 7).
Write the invoice to Excel with Apache POI (see Excel with Apache POI ).
Use BigDecimal for exact money arithmetic.
Next steps
Learn a build tool (Maven or Gradle) to manage libraries, write unit tests with JUnit, and explore Spring Boot for web services.
That’s the Java course.
Code for this course follows standard, current syntax; we test JavaScript and PowerShell scripts before publishing, and R/Java/Rust examples are kept to core language features. Tell us if anything fails on your setup.
Practice
Run Invoice.java and add one of the extensions.
← Java Lesson 7: Exceptions and Files 📎 Practice files for this article Free to use for learning. Files with macros (.bas) are plain text — import them with Alt +F11 → File → Import File, and always test on a copy.
Written by Atul Vij Atul (AJ) builds office-automation and local-first AI tools as Atulya AI, and works with Excel, SAP and Oracle EPM every day. He writes about the shortcuts, macros and automations that actually save time — plus the occasional wacky fact. Videos on YouTube: Lazy Automator AI (@LazyAutomatorAI).
More posts by Atul → ← Previous Java Lesson 7: Exceptions and FilesNext → Java Streams for Beginners: filter, map and collect Explained✨ Ask AI about this article Stuck on a step? Ask a question and the AI answers using this article.
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