Refactoring Java Code with TDD and SOLID Principles

Writing working Java code is only the first step; writing code that is easy to maintain, extend, and test is where true software craftsmanship begins. If you have ever struggled to modify existing code without breaking other parts of your application, mastering refactoring is your next critical step. This text-only course guides you through the process of transforming brittle, hard-to-maintain Java code into a clean, extensible system using shape area calculation as a practical model. You will learn how to apply Test-Driven Development (TDD) and SOLID design principles to restructure your code confidently. What you'll learn: Understand the core concepts of SOLID design and how they prevent code rot; Write clean unit tests using JUnit to guide your refactoring process; Apply abstract classes and interfaces to make your code open for extension but closed for modification; Identify common code smells in Java and systematically resolve them; Implement modern Java features like records and pattern matching for cleaner object structures; Refactor step-by-step using red-green-refactor cycles without breaking existing functionality. You will start by exploring foundational software design principles and identifying flaws in a typical, naive shape calculation program. From there, you will read through step-by-step refactoring exercises, building a robust, test-backed solution from the ground up. This course is designed for beginner Java developers who understand basic syntax and want to transition to writing professional-grade, clean code. No prior testing or refactoring experience is required. Start reading today to elevate your programming skills and build software that stands the test of time.