Welcome to Rx. This book is based on [Rx.NET](http://msdn.microsoft.com/en-us/devlabs/gg577609)'s www.introtorx.com and it introduces beginners to [RxJava](https://github.com/ReactiveX/RxJava), the Netflix implementation of the original Microsoft library. Rx is a powerful tool that enables the solution of problems in an elegant declarative style, familiar to functional programmers. Rx has several benefits:

* Unitive

* Queries in Rx are done in the same style as other libraries inspired by functional programming, such as Java streams. In Rx, one can use functional style transformations on event streams.

* Extensible

* RxJava can be extended with custom operators. Although Java does not allow for this to happen in an elegant way, RxJava offers all the extensibility one can find Rx implementations in other languages.

* Declarative

* Functional transformations are read in a declarative way.

* Composable

* Rx operators can be combined to produce more complicated operations.

* Transformative

* Rx operators can transform one type of data to another, reducing, mapping or expanding streams as needed.

Rx is fit for composing and consuming sequences of events. We present some of the use cases for Rx, according to www.introtorx.com

* UI events like mouse move, button click

* Domain events like property changed, collection updated, "Order Filled", "Registration accepted" etc.

* Infrastructure events like from file watcher, system and WMI events

* Integration events like a broadcast from a message bus or a push event from WebSockets API or other low latency middleware like Nirvana

* Integration with a CEP engine like StreamInsight or StreamBase.

* Result of `Future` or equivalent pattern

Those patterns are already well adopted and you may find that introducing Rx on top of that does not add to the development process.

* Translating iterables to observables, just for the sake of working on them through an Rx library.

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