In the previous chapter, we took a detailed look at the problems associated with modularizing Java code pre-Java 9, as well as the new module construct in Java 9 and Project Jigsaw. Before we examine how Java modularity solves these problems, you'll need to first understand what a Java module looks like. In this chapter, you'll create your first Java 9 module and learn what it takes to build and execute code in a Java module. Here are the top-level topics you'll be learning in this chapter:

• Setting up the JDK with Java 9
• Creating a new Java 9 module
• Defining a module (using module-info.java)
• Compiling and executing a module
• Handling possible errors

You'll be building a sample Java 9 application throughout this book as you learn the different concepts related to modularity. The application you'll build is an address book viewer application that displays some contacts sorted by last name. We'll start simple and enhance this application as we go. When you are done with this chapter, you'll have built your first Java 9 module and learned how to compile and execute it. Let's start by first installing the JDK.