In this chapter, we examined the structure of Java modules as specified by Project Jigsaw and took an in-depth look at how Project Jigsaw was implemented to improve the Java platform. We also reviewed key internal changes to the Java platform as they relate to the modular system. Our review started with a modular primer, where we learned about Java's modular system in terms of benefits and requirements.

We explored the seven primary tool categories that make up the JDK. As we learned, modularity in Java also extends to runtime images resulting in more maintainability, better performance, and increased security. The concept of link time was introduced as an optional phase between compile-time and runtime. We concluded the chapter with a look at the Java Linker and how Java encapsulates internal APIs.

In the next chapter, we will explore how to migrate our existing applications to the current Java platform. We will look at both manual and semi-automated migration processes.