Chapter 1, RX – from .NET to RxJava, takes initial steps into the reactive world. We will compare the reactive approach with the classic approach, and will explore the similarities and differences between them.

Chapter 2, Why Observables?, gives an overview of the Observer pattern, how it's implemented and extended by RxJava, what an Observable is, and how Observables relate to Iterables.

Chapter 3, Hello Reactive World, uses what we have learned so far to create our first reactive Android app.

Chapter 4, Filtering Observables, dives into the essence of an Observable sequence: filtering. We will also learn how to select only the values we want from an emitting Observable, how to obtain a finite number of values, how to handle overflow scenarios, and a few more useful tricks.

Chapter 5, Transforming Observables, shows how to transform Observable sequences to create sequences that can fit our needs.

Chapter 6, Combining Observables, digs into combining functions, and we are going to learn how to work with multiple Observables simultaneously when we create the Observable we want.

Chapter 7, Schedulers – Defeating the Android MainThread Issue, shows you how to work with multithreading and concurrent programming using RxJava Schedulers. We will create network operations, memory accesses, and time-consuming tasks in a reactive way.

Chapter 8, REST in Peace – RxJava and Retrofit, teaches you how Retrofit by Square can be used with RxJava to create an REST client efficiently and effectively.

To run the examples in this book, you will need a standard Android development environment:

As you are approaching RxJava as a pure Java developer, you will obviously need your preferred Java editor and a standard Java JDK environment. Some of the figures used in this book are taken from http://rxmarbles.com/ and http://reactivex.io/.

If you are an experienced Java developer, reactive programming will give you a new way to approach scalability and concurrency in your backend systems, without forcing you to switch to change the programming languages. This book will help you learn the core aspects of RxJava and will also help you overcome the limitations of the Android platform to create event-driven, reactive, and smooth Android applications.

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "As you can see, zip() has three parameters: the two Observables and Func2, as expected."

A block of code is set as follows:

public Observable<List<User>> getMostPopularSOusers(int howmany) {
        return mStackExchangeService
              .getMostPopularSOusers(howmany)
                .map(UsersResponse::getUsers)
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread());
    }

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

public Observable<List<User>> getMostPopularSOusers(int howmany) {
        return mStackExchangeService
              .getMostPopularSOusers(howmany)
                .map(UsersResponse::getUsers)
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread());
    }

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "We will just need a fancy progress bar and a DOWNLOAD button."

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