Most veteran Java programmers would acknowledge that it has been a while since they have created folder structures by hand for their Java projects. The Java language has benefitted from incredibly useful tooling support over the years. IDEs such as Eclipse, NetBeans, and IntelliJ IDEA make it such a breeze to create source and package folders that developers don't even tend to think about those aspects of code organization too often. However, in this chapter, and in fact in the rest of the book, we will learn how to build folders and files by hand, as well as compile and run the code by executing commands manually from the command line. This is because IDEs, as convenient as they might be, tend to hide the details and workings around the process of structuring and compiling code. We intend to examine how Java 9 modules work, and the fundamental workings of the code structure, as well as compiling and linking commands, are essential to mastering these concepts.

While the prospect of writing Java code without an IDE might seem daunting, let me assure you that this is something you'll likely get used to very quickly. You'll learn the steps to build and execute modular Java 9 code in this chapter, and then it's just a matter of applying the same steps independent of the complexity of the code base itself.