Chapter 1. An Introduction to Reactive Programming

Nowadays, the term reactive programming is trending. Libraries and frameworks in various programming languages are emerging. Blog posts, articles and presentations about reactive programming are being created. Big companies, such as Facebook, SoundCloud, Microsoft, and Netflix, are supporting and using this concept. So we, as programmers, are starting to wonder about it. Why are people so excited about reactive programming? What does it mean to be reactive? Would it be helpful in our projects? Should we learn how to use it?

Meanwhile, Java is popular with its multi-threading, speed, reliability, and good portability. It is used for building a wide variety of applications, from search engines, through databases to complex web applications running on server clusters. But Java has bad reputation too—it is very hard to write both concurrent and simple applications using only the built-in tools, and programming in Java requires writing a lot of boilerplate code. Also, if you need to be asynchronous (using futures, for example), you can easily get into "callback hell", which actually holds true for all programming languages.

In other words, Java is powerful and you can create great applications with it, but it won't be easy. The good news is that there is a way to change that, using the reactive style of programming.

This book will present RxJava (https://github.com/ReactiveX/RxJava), an open source Java implementation of the reactive programming paradigm. Writing code using RxJava requires a different kind of thinking, but it will give you the power to create complex logic using simple pieces of well-structured code.

In this chapter, we will cover: