Clean Code in Java 🧹

An educational Maven project demonstrating common code smells and their refactoring solutions in Java with practical, real-world examples.

📋 Table of Contents

• Project Overview
• Prerequisites
• Project Structure
• Quick Start
• Available Code Smells
• Running Instructions
• Testing
• Contributing

🎯 Project Overview

This project serves as an educational resource for learning clean code principles through hands-on examples. Each code smell is demonstrated with:

• ✅ Before and after code comparisons
• ✅ Interactive console demonstrations
• ✅ Unit tests showing improvements

📋 Available Code Smells

Size & Complexity Problems

• Long Method: Extract Method refactoring to break down complex methods
• Long Parameter List: Introduce Parameter Object refactoring to group related parameters
• Magic Numbers: Replace Magic Number with Named Constant refactoring to improve readability

OOP Anti-Patterns

• Switch Statements: Replace Conditional with Polymorphism to eliminate switch statements

Dependency Problems

• Feature Envy: Move Method refactoring to place methods with the data they operate on
• Circular Dependencies: Dependency Inversion refactoring to break circular dependencies with interfaces

🔧 Prerequisites

• Java 21 (OpenJDK 21.0.7+)
• Maven 3.9+
• IDE (IntelliJ IDEA, Eclipse, or VS Code recommended)

Installing Java 21

# Using SDKMAN (recommended)
sdk install java 21.0.7-tem

# For this project only (recommended approach)
# The project includes .sdkmanrc file for automatic environment switching
sdk env

# Or manually switch for this session only
sdk use java 21.0.7-tem

# Verify installation
java --version

📁 Project Structure

clean-code/
└── src/main/java/com/cleancode/
    ├── domain/
    ├── sizecomplexity/
    │   ├── longmethod/
    │   ├── longparameterlist/
    │   └── magicnumbers/
    ├── oopantipatterns/
    │   └── switchstatements/
    ├── dependencyproblems/
    │   ├── featureenvy/
    │   └── circulardependencies/
    └── Main.java

Code Smell Organization:

• Each code smell has its own dedicated package
• Clear separation between problematic and refactored code
• Shared domain models in com.cleancode.domain package
• Comprehensive test coverage for each smell

🚀 Quick Start

1. Clone the Repository

git clone https://github.com/shift-elevate/clean-code.git
cd clean-code

2. Setup Environment (Automatic with SDKMAN)

The project includes a .sdkmanrc file that automatically configures Java 21 and Maven when you enter the directory:

# Activate the project environment (Java 21 + Maven)
sdk env

# This will automatically switch to:
# - Java 21.0.7-tem
# - Maven 3.9.10

3. Build the Project

mvn clean compile

4. Run the Main Application

mvn exec:java -Dexec.mainClass="com.cleancode.Main"

This will launch the main demonstration showing all implemented code smells and their refactored solutions.

📚 Running Instructions

🎯 Recommended: Run Main Application for Complete Demo

The best way to see all code smells and refactoring solutions in action:

# Run the main application with all demonstrations
mvn exec:java -Dexec.mainClass="com.cleancode.Main"

# Or compile and run directly
mvn clean compile
java -cp target/classes com.cleancode.Main

📦 Advanced: Build and Run JAR

For standalone execution:

# Build executable JAR
mvn clean package

# Run the JAR
java -jar target/clean-code-java-1.0.0.jar

🧪 Testing

Run All Tests

mvn test

Run Individual Code Smell Demonstrations

# Long Method Code Smell
mvn exec:java@long-method

# Switch Statements Code Smell
mvn exec:java@switch-statements

# Long Parameter List Code Smell
mvn exec:java@long-parameter-list

# Magic Numbers Code Smell
mvn exec:java@magic-numbers

# Feature Envy Code Smell
mvn exec:java@feature-envy

# Circular Dependencies Code Smell
mvn exec:java@circular-dependencies

Note: Each execution ID runs only the specific code smell demonstration, not all of them.

Run All Code Smells Together

# Run the main application with all demonstrations
mvn exec:java -Dexec.mainClass="com.cleancode.Main"

Run Specific Test Class

# Long Method Code Smell
mvn test -Dtest=LongMethodTest

# Long Parameter List Code Smell
mvn test -Dtest=LongParameterListTest

# Magic Numbers Code Smell
mvn test -Dtest=MagicNumbersTest

# Switch Statements Code Smell
mvn test -Dtest=SwitchStatementsTest

# Feature Envy Code Smell
mvn test -Dtest=FeatureEnvyTest

# Circular Dependencies Code Smell
mvn test -Dtest=CircularDependenciesTest

🐛 Troubleshooting

Common Issues

Java Version Issues:

# Check Java version
java --version

# Ensure Java 21 is active
sdk current java

Maven Compilation Issues:

# Clean and rebuild
mvn clean compile

# Skip tests if needed
mvn compile -DskipTests

Class Path Issues:

# Ensure proper classpath when running
java -cp target/classes com.cleancode.Main