In this chapter, we learned to refactor existing code to take full advantage of object-oriented code with Java 9. We have prepared the code for future requirements, reduce maintenance costs, and maximized code reuse.

We learned to organize object-oriented code. We created many Java source files. We declared interfaces, abstract classes, and concrete classes in different Java source files. We took advantage of the new modularity features included in Java 9 to create many modules that have dependencies on different modules and exported specific types. We learned to declare modules, compile them to Java bytecode, and launch an application outside of JShell.

Now that you have learned to write object-oriented code in Java 9, you are ready to use everything you learned in real-life desktop applications, mobile apps, enterprise applications, Web Services, and web applications. These applications will maximize code reuse, simplify maintenance, and they will be always ready for future requirements...