The content of this book is based on Play 2.3.x and shows both Scala and Java APIs. Though this book uses Java 8, Play supports Java 6, so all you need to start developing a Play application is at least JDK 6. Chapter 1, Building a Web Service, explains how to install activator, a command-line tool to generate starter application skeletons and then manage their life cycle (running, testing, and so on). Finally, you also need a web browser to use your applications.