ChaiCode Java Labs

Master Java fundamentals through 47 real-world, story-based challenges. Each exercise puts you in a practical scenario — cinema ticketing, ATM withdrawals, email validation, and more.

279 JUnit tests across 10 topics

Edit the Java files on your machine and run tests with Maven. Only edit files under src/main/java/ — never change the test files.

Prerequisites

Everything you need before opening the project.

Required

Requirement	Minimum version	Why you need it
Java JDK	17 or higher	Compiles and runs the lab code
Internet connection	—	First Maven run downloads JUnit and dependencies
Terminal	—	PowerShell, Command Prompt, or Mac/Linux terminal

Optional (recommended)

Tool	Why it helps
VS Code or IntelliJ IDEA	Edit Java with syntax highlighting and one-click test runs
Extension Pack for Java (VS Code)	Run individual tests from the editor
Git	Version control for your solutions

You do NOT need

Tool	Reason
Maven installed globally	This project includes `mvnw` / `mvnw.cmd` (Maven Wrapper)
Paid IDE license	IntelliJ Community Edition is free and works fine

System requirements

Windows 10/11, macOS, or Linux
~200 MB disk space (more after first Maven build in target/)
JDK 17+ from Adoptium or Oracle

Setup guide

Follow these steps once before you start solving challenges.

Step 1 — Install Java JDK 17+

Windows

Download JDK 17+ from Adoptium
Run the installer (keep default options)
Restart your terminal and IDE after install

macOS

brew install openjdk@17

Or download from Adoptium and install the .pkg.

Linux (Ubuntu/Debian)

sudo apt update
sudo apt install openjdk-17-jdk

Step 2 — Verify Java is installed

Open a terminal and run:

java -version

You should see output like:

openjdk version "17.0.x" ...

Also check the compiler:

javac -version

If either command is not found, Java is not on your PATH. Reinstall JDK or add JAVA_HOME to your environment variables.

Windows — set JAVA_HOME (if IDE cannot find Java)

Search Environment Variables in Windows
Add a new system/user variable:
- Name: JAVA_HOME
- Value: C:\Program Files\Eclipse Adoptium\jdk-17.x.x-hotspot (your actual JDK path)
Add %JAVA_HOME%\bin to your Path variable
Restart terminal and IDE

Step 3 — Get the project on your machine

If you already have the folder, skip to Step 4.

# Example — clone or copy the project folder
cd C:\coding-room
# Your project should be at:
# C:\coding-room\chaicode-java-labs

Step 4 — Open the project

VS Code

File → Open Folder
Select chaicode-java-labs (the folder that contains pom.xml)
Install Extension Pack for Java when prompted
Wait for the Java language server to finish loading (status bar bottom-right)

IntelliJ IDEA

File → Open
Select the chaicode-java-labs folder
IntelliJ detects Maven automatically — click Load Maven Project if asked

Step 5 — First build (download dependencies)

Open a terminal in the project root (where pom.xml lives).

Windows (PowerShell or Command Prompt)

cd C:\coding-room\chaicode-java-labs
.\mvnw.cmd test

macOS / Linux

cd /path/to/chaicode-java-labs
chmod +x mvnw
./mvnw test

What to expect on first run

Maven downloads JUnit and plugins (1–3 minutes depending on network)
You will see many failing tests — this is normal
Your job is to implement the methods and make tests pass

Successful first run looks like:

Tests run: 279, Failures: ..., Errors: ...
BUILD SUCCESS   ← build succeeded (tests may still fail until you write code)

If the build itself fails (compile errors, Maven not found), see Troubleshooting.

Step 6 — Fix PowerShell execution policy (Windows only, if needed)

If you see:

.\mvnw.cmd cannot be loaded because running scripts is disabled

Run once:

Set-ExecutionPolicy -Scope CurrentUser RemoteSigned

Or use Command Prompt instead:

cd C:\coding-room\chaicode-java-labs
mvnw.cmd test

Step 7 — Confirm you are in the right folder

Your terminal should list these files:

pom.xml
mvnw.cmd        (Windows) or mvnw (Mac/Linux)
README.md
src/

Always run Maven commands from this folder, not from src/.

How to run tests

All commands below assume you are in the project root.

Windows: use .\mvnw.cmd
macOS / Linux: use ./mvnw

Run ALL tests (entire lab)

Runs every test class in the project (279 tests).

.\mvnw.cmd test

./mvnw test

Use this to check overall progress after completing several challenges.

Example output when done:

Tests run: 279, Failures: 0, Errors: 0, Skipped: 0
BUILD SUCCESS

Run ONE challenge (entire test class)

Each challenge has one test class, e.g. EmployeeBadgeTest for EmployeeBadge.java.

.\mvnw.cmd test -Dtest=EmployeeBadgeTest

./mvnw test -Dtest=EmployeeBadgeTest

More examples:

.\mvnw.cmd test -Dtest=TicketPricingTest
.\mvnw.cmd test -Dtest=ShoppingCartTotalTest
.\mvnw.cmd test -Dtest=PalindromeCheckerTest
.\mvnw.cmd test -Dtest=LoanEMITest

This is the recommended way to work — solve one challenge, run its test class, then move on.

Run a SINGLE test case (one test method)

Use ClassName#methodName to run exactly one test.

.\mvnw.cmd test -Dtest=EmployeeBadgeTest#managerBadge

./mvnw test -Dtest=EmployeeBadgeTest#managerBadge

More examples:

.\mvnw.cmd test -Dtest=TicketPricingTest#childAge5Weekday
.\mvnw.cmd test -Dtest=PrimeCheckerTest#seventeenIsPrime
.\mvnw.cmd test -Dtest=RestaurantBillTest#standardBill

Use this when debugging one failing case without running the whole class.

Run MULTIPLE challenges (several test classes)

Separate class names with commas (no spaces).

.\mvnw.cmd test -Dtest=EmployeeBadgeTest,ProductListingTest,FitnessProfileTest

./mvnw test -Dtest=EmployeeBadgeTest,ProductListingTest,FitnessProfileTest

Run all tests in one topic (wildcard):

# All variables challenges
.\mvnw.cmd test -Dtest=com.chaicode.variables.*Test

# All conditionals challenges
.\mvnw.cmd test -Dtest=com.chaicode.conditionals.*Test

# All for-loop challenges
.\mvnw.cmd test -Dtest=com.chaicode.forloop.*Test

Run multiple specific methods from the same class:

.\mvnw.cmd test -Dtest=EmployeeBadgeTest#managerBadge+staffBadge

Quick reference — testing commands

Goal	Command (Windows)
Run all tests	`.\mvnw.cmd test`
Run one challenge	`.\mvnw.cmd test -Dtest=EmployeeBadgeTest`
Run one test case	`.\mvnw.cmd test -Dtest=EmployeeBadgeTest#managerBadge`
Run multiple challenges	`.\mvnw.cmd test -Dtest=TestA,TestB,TestC`
Run whole topic	`.\mvnw.cmd test -Dtest=com.chaicode.variables.*Test`
Compile only (no tests)	`.\mvnw.cmd compile`
Clean + full test run	`.\mvnw.cmd clean test`

On Mac/Linux, replace .\mvnw.cmd with ./mvnw.

Run tests from your IDE

VS Code

Open a test file, e.g. src/test/java/com/chaicode/variables/EmployeeBadgeTest.java
Click Run Test above a @Test method (single case)
Click Run Tests above the class name (whole challenge)
Or open the Testing sidebar (flask icon) and run from there

IntelliJ IDEA

Open a test file
Green ▶ next to a method → run one test case
Green ▶ next to the class name → run all tests in that class
Right-click src/test/java → Run 'All Tests' for the full lab

Topics covered

Topic	Package	Challenges	Concepts
Variables & Data Types	`variables`	3	`int`, `double`, `boolean`, `String`, records
Operators	`operators`	4	Arithmetic, comparison, logical, compound
Conditionals	`conditionals`	12	`if/else`, `switch`, ternary, validation
For Loop	`forloop`	4	Summation, factorial, primes, FizzBuzz
While Loop	`whileloop`	4	Digit manipulation, savings planner, ATM
Do-While Loop	`dowhileloop`	3	Survey input, PIN retry, order counting
Scanner	`scanner`	3	`java.util.Scanner`, parsing input
Methods	`methods`	4	Parameters, return types, overloading patterns
Arrays (1D & 2D)	`arrays`	5	Search, stats, matrices, gradebook
Strings & StringBuilder	`strings`	5	`String` methods, `StringBuilder`, validation

Suggested learning order

Variables → EmployeeBadge.java, ProductListing.java, FitnessProfile.java
Operators → RestaurantBill.java, SaleDiscount.java, TimeBreakdown.java, GameScoreComparer.java
Conditionals → TicketPricing.java through SeasonActivity.java (12 challenges)
For Loop → ShoppingCartTotal.java, FactorialCalculator.java, PrimeChecker.java, FizzBuzzCounter.java
While Loop → ATMWithdrawal.java, DigitSum.java, ReverseDigits.java, SavingsPlanner.java
Do-While Loop → SurveyAverage.java, PinValidator.java, PizzaOrders.java
Scanner → CafeOrder.java, StudentRegistration.java, SimpleCalculator.java
Methods → GeometryAreas.java, TemperatureConverter.java, LoanEMI.java, GreetingGenerator.java
Arrays → ClassroomStats.java, InventorySearch.java, CinemaSeats.java, MatrixAddition.java, GradebookAverage.java
Strings → PalindromeChecker.java, EmailValidator.java, SlugBuilder.java, TitleCase.java, CreditCardMask.java

Project structure

chaicode-java-labs/
├── pom.xml
├── mvnw / mvnw.cmd
├── README.md
│
├── src/main/java/com/chaicode/
│   ├── variables/          ← YOU EDIT THESE
│   ├── operators/
│   ├── conditionals/       (12 real-world stories from ChaiCode)
│   ├── forloop/
│   ├── whileloop/
│   ├── dowhileloop/
│   ├── scanner/
│   ├── methods/
│   ├── arrays/
│   └── strings/
│
└── src/test/java/com/chaicode/
    └── ...                 ← DO NOT EDIT (JUnit tests)

How to solve a challenge

Open a challenge file (e.g. src/main/java/com/chaicode/variables/EmployeeBadge.java)
Read the Javadoc at the top — it explains the story, rules, and return values
Replace // Your code here with your implementation
Run that challenge's tests:

.\mvnw.cmd test -Dtest=EmployeeBadgeTest

If one test fails, run just that case to debug:

.\mvnw.cmd test -Dtest=EmployeeBadgeTest#managerBadge

When all tests in the class pass, move to the next challenge

Conditionals challenges (from ChaiCode)

#	Class	Test class	Story
01	`TicketPricing`	`TicketPricingTest`	Starlight Cinema ticket pricing
02	`TrafficLight`	`TrafficLightTest`	SafeDrive traffic light simulator
03	`GradeCalculator`	`GradeCalculatorTest`	Ms. Parker's report cards
04	`WeatherAdvice`	`WeatherAdviceTest`	TrailBuddy hiking app
05	`LibraryCard`	`LibraryCardTest`	Maple Town Library
06	`ShippingCalculator`	`ShippingCalculatorTest`	ShopSwift store shipping
07	`CoffeeShop`	`CoffeeShopTest`	Bean & Brew Cafe
08	`TaxCalculator`	`TaxCalculatorTest`	Sam's freelance taxes
09	`PasswordStrength`	`PasswordStrengthTest`	SecureApp signup
10	`TipCalculator`	`TipCalculatorTest`	TipEasy restaurant
11	`ParkingFee`	`ParkingFeeTest`	City Central Parking
12	`SeasonActivity`	`SeasonActivityTest`	WanderLust Travel

Troubleshooting

`'java' is not recognized`

Install JDK 17+ from Adoptium
Set JAVA_HOME and add %JAVA_HOME%\bin to Path
Restart terminal and IDE

`'mvn' is not recognized`

You do not need global Maven. Always use:

.\mvnw.cmd test

Not mvn test.

PowerShell blocks `mvnw.cmd`

Set-ExecutionPolicy -Scope CurrentUser RemoteSigned

Or use Command Prompt: mvnw.cmd test

First run is slow or fails on network

Check internet connection
Retry: .\mvnw.cmd test
Corporate proxy may require Maven proxy settings

All tests fail with `expected X but was 0` or `was ""`

Normal before you write solutions. Implement the method in the challenge file.

`NullPointerException` in tests

Some challenges return objects (BorrowResult, StudentInfo, etc.). Your method is still returning null — finish the implementation.

VS Code does not show Run Test buttons

Install Extension Pack for Java
Reload: Ctrl+Shift+P → Developer: Reload Window
Open the folder that contains pom.xml

IntelliJ shows red errors but `mvnw test` works

File → Invalidate Caches → Invalidate and Restart, or right-click pom.xml → Maven → Reload project

Test reports on disk

After a test run, detailed reports are in:

target\surefire-reports\

Progress checklist

Variables & Data Types

EmployeeBadge
ProductListing
FitnessProfile

Operators

RestaurantBill
SaleDiscount
TimeBreakdown
GameScoreComparer

Conditionals

TicketPricing … SeasonActivity (12 total)

Loops

ShoppingCartTotal, FactorialCalculator, PrimeChecker, FizzBuzzCounter
ATMWithdrawal, DigitSum, ReverseDigits, SavingsPlanner
SurveyAverage, PinValidator, PizzaOrders

Scanner

CafeOrder, StudentRegistration, SimpleCalculator

Methods

GeometryAreas, TemperatureConverter, LoanEMI, GreetingGenerator

Arrays

ClassroomStats, InventorySearch, CinemaSeats, MatrixAddition, GradebookAverage

Strings

PalindromeChecker, EmailValidator, SlugBuilder, TitleCase, CreditCardMask

Good luck — start with EmployeeBadge.java and run .\mvnw.cmd test -Dtest=EmployeeBadgeTest!

Name		Name	Last commit message	Last commit date
.mvn/wrapper		.mvn/wrapper
src		src
.gitignore		.gitignore
README.md		README.md
mvnw		mvnw
mvnw.cmd		mvnw.cmd
pom.xml		pom.xml

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