Book Image

Learning RxJava

By : Thomas Nield
Book Image

Learning RxJava

By: Thomas Nield

Overview of this book

RxJava is a library for composing asynchronous and event-based programs using Observable sequences for the JVM, allowing developers to build robust applications in less time. Learning RxJava addresses all the fundamentals of reactive programming to help readers write reactive code, as well as teach them an effective approach to designing and implementing reactive libraries and applications. Starting with a brief introduction to reactive programming concepts, there is an overview of Observables and Observers, the core components of RxJava, and how to combine different streams of data and events together. You will also learn simpler ways to achieve concurrency and remain highly performant, with no need for synchronization. Later on, we will leverage backpressure and other strategies to cope with rapidly-producing sources to prevent bottlenecks in your application. After covering custom operators, testing, and debugging, the book dives into hands-on examples using RxJava on Android as well as Kotlin.
Table of Contents (21 chapters)
Title Page
Credits
About the Author
Acknowledgements
About the Reviewers
www.PacktPub.com
Customer Feedback
Preface

Understanding multicasting


We have used the ConnectableObservable earlier in Chapter 2Observables and Subscribers. Remember how cold Observables, such as Observable.range(), will regenerate emissions for each Observer? Let's take a look at the following code:

import io.reactivex.Observable;

public class Launcher {
    public static void main(String[] args) {

        Observable<Integer> threeIntegers  = Observable.range(1, 3);

        threeIntegers.subscribe(i -> System.out.println("Observer One: " + i));
        threeIntegers.subscribe(i -> System.out.println("Observer Two: " + i));
    }
}

The output is as follows:

Observer One: 1
Observer One: 2
Observer One: 3
Observer Two: 1
Observer Two: 2
Observer Two: 3

Here, Observer One received all three emissions and called onComplete(). After that, Observer Two received the three emissions (which were regenerated again) and called onComplete(). These were two separate streams of data generated for two separate subscriptions. If we...