Introduction to Reactive Programming with RxJava

RxJava is a Java VM implementation of ReactiveX, a library for composing asynchronous and event-based programs by using observable sequences. It is used for reactive programming which I like to refer as “programming with asynchronous data streams” or “programming waiting for something happens to trigger your code” or “programming to react undetermined events”

I’m gonna be straightfoward because this topic it is a well known case that you only learn by doing. Basically, this is how it works: A Subscriber subscribes to Observable, then Observable calls Subscriber.onNext() for any number of items, if something goes wrong here is Subsciber.onError() and if all finishes fine, here is Subscriber.onCompleted().

The foundations

Subscribers -> It listens to the events/items;

Observables -> It emits events/items - This class provides methods for subscribing to the Observable as well as delegate methods to the various Observers. It is necessary to trigger/listen/activate/start the observables otherwise they don’t do anything;

Operators -> Functions responsible for manipulate observables. It can applyed along other operators and it has seveval goals: creation, combination, transformation, filtering, etc;

Schedulers -> It manages the work with thread pools via Executors (java.util.concurrent);

Transforming Streams with operators

As it was said before, operators can manipulate observables. There are plenty of them and it is really important to know how/when use them. Here is the most popular RxJava operators:

Further details

I totally recommend this talk by Jake Wharton, an outstanding developer and a reference in opensource projects. Another option is watch this video but don’t forget to practice, try to implement what it is suggested in the video.