This course will teach you how to practically apply SOLID principles in modern Java applications to avoid technical debt and build robust, loosely coupled systems that can evolve easily over time.

Object-oriented code can become fragile and difficult to extend without clear structure. In this course, Java SE Deep Dive: Refactoring to SOLID Java, you'll learn to refactor applications by applying SOLID object-oriented principles to make them more robust and easier to maintain. First, you'll explore the Single Responsibility Principle (SRI), and why this is probably the most important concept in programming. Next, you'll discover the Open-closed Principle (OCP), and learn how to evolve applications without altering existing code. After that, you'll explore the Liskov Substitution Principle (LSP) and find out how to create correct relationships using inheritance. Then, you'll see why it's not a good idea to create "fat" interfaces, and change that using the Interface Segregation Principle (ISP). Finally, you'll learn how to create loosely coupled components by applying the Dependency Inversion Principle (DIP). When you're finished with this course, you'll have the skills and knowledge of building code that respects the SOLID principles needed to build loosely coupled applications that are easy to understand, evolve, and maintain.