Workshop – Contact Management App

The Scenario

You are building a console-based contact management application.

Think about what a contact manager should do and how a user would interact with it — then build it.

Create ContactApp.java inside src/main/java/se/lexicon/.
Commit regularly as you make progress.

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Requirements

Before writing any code, think through the following:

• Functionality — what operations should a contact manager support? What would a user expect to be able to do?
• Data — what information does a contact hold? How should that be represented given your chosen data structure?
• Data structure — which structure fits the way contacts will be stored and accessed? Consider the trade-offs.
• Constraints — what rules should the system enforce? Think about what invalid states should never be allowed.
• Code organisation — how will you separate concerns? Each operation should have a clear home in your code.

Programing Principles to keep in mind:

• SRP (Single Responsibility) — each class and method should have one clear job.
• Separation of Concerns — keep your menu logic, your data storage, and your business rules in separate places.
• KISS (Keep It Simple) — prefer a straightforward solution over a clever one. If it's hard to explain, it's probably too complex.
• DRY (Don't Repeat Yourself) — if you find yourself writing the same logic in more than one place, extract it into a method.
• YAGNI (You Aren't Gonna Need It) — don't build features that haven't been asked for. Solve today's problem first.

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Optional Challenges

Once the core app works, try extending it:

• create a new branch for each challenge
• commit your work regularly
• merge your branch into the main branch when you're done

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Challenge 1 – Sort Contacts

Display all contacts sorted alphabetically by name.

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Challenge 2 – Unit Tests

Write unit tests for each data-access operation: add, search, delete, and update.

• Use JUnit 5 and place tests in src/test/java/se/lexicon/
• Each method should have at least one positive test case and one negative test case

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Challenge 3 – File I/O

Export: Save all contacts to a file when the user exits.
Import: Load contacts from that file automatically when the app starts.

Support at least one format:

• Plain text — one contact per line, in a format that matches your storage approach
• CSV
• Excel (.xlsx)

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Submission

Push your project to GitHub and share the repository link with your instructor.