Chapter 9. Refactoring, testing, and debugging

In the first eight chapters of this book, you saw the expressive power of lambdas and the Streams API. You were mainly creating new code that used these features. If you have to start a new Java project, you can use lambdas and streams immediately.

Unfortunately, you don’t always get to start a new project from scratch. Most of the time you have to deal with an existing code base written in an older version of Java.

This chapter presents several recipes that show you how to refactor existing code to use lambda expressions to gain readability and flexibility. In addition, we discuss how several object-oriented design patterns (including strategy, template method, observer, chain of responsibility, and factory) can be made more concise thanks to lambda expressions. Finally, we explore how you can test and debug code that uses lambda expressions and the Streams API.

In chapter 10, we explore a more wide-ranging way of refactoring code to make the application logic more readable: creating a domain-specific language.

9.1. Refactoring for improved readability and flexibility

9.2. Refactoring object-oriented design patterns with lambdas

9.3. Testing lambdas

9.4. Debugging

Summary