Part 1. Hello, modules

Java 9 makes modularity a first-class concept. But what are modules? Which problems do they solve, and how can you benefit from them? And what does first-class mean?

The book you’re reading will answer all of these questions and more. It teaches you how to define, build, and run modules, what impact they have on existing projects, and what benefits they provide.

All in due time, though. This part of the book starts by explaining what modularity means, why it’s direly needed, and what the module system’s goals are (chapter 1). Chapter 2 throws you into the deep end and shows code that defines, builds, and runs modules, before chapters 3–5 explore those three steps in detail. Chapter 3 is particularly important because it introduces the basic concepts and mechanisms underlying the module system.

Part 2 of the book discusses the challenges Java 9 incurs for existing applications, and part 3 introduces more-advanced features.