Book Image

Modular Programming in Java 9

By : Koushik Srinivas Kothagal
Book Image

Modular Programming in Java 9

By: Koushik Srinivas Kothagal

Overview of this book

The Java 9 module system is an important addition to the language that affects the way we design, write, and organize code and libraries in Java. It provides a new way to achieve maintainable code by the encapsulation of Java types, as well as a way to write better libraries that have clear interfaces. Effectively using the module system requires an understanding of how modules work and what the best practices of creating modules are. This book will give you step-by-step instructions to create new modules as well as migrate code from earlier versions of Java to the Java 9 module system. You'll be working on a fully modular sample application and add features to it as you learn about Java modules. You'll learn how to create module definitions, setup inter-module dependencies, and use the built-in modules from the modular JDK. You will also learn about module resolution and how to use jlink to generate custom runtime images. We will end our journey by taking a look at the road ahead. You will learn some powerful best practices that will help you as you start building modular applications. You will also learn how to upgrade an existing Java 8 codebase to Java 9, handle issues with libraries, and how to test Java 9 applications.
Table of Contents (19 chapters)
Title Page
Credits
About the Author
About the Reviewers
www.PacktPub.com
Customer Feedback
Preface

Revisiting classpath


We've seen that the new Java 9 platform comes with some new abilities to do module level compilation and execution using the --module-source-path and the --module-path arguments. It is now module-aware and knows what to do in order to compile and execute Java 9 modules. It's very likely that these flags are going to find increased usage as developers embrace Java modularity.

At the same time, there's a familiar compiler parameter that will, over time, see decreased usage--the -classpath parameter. The classpath that has been a concept that's essential to programming in Java for so many years, is for the most part, not required anymore!

For about two decades now, the Java classpath has played the crucial role of being the home for all the classes in any given Java application. Any Java application is obviously made up of multiple classes, often in multiple jar files. As a Java developer, all you had to do to get a class into play was to add it to the classpath. That would...