RxJava is a Java VM implementation of ReactiveX (Reactive Extensions): a library for composing asynchronous and event-based programs by using observable sequences.

For more information about ReactiveX, see the Introduction to ReactiveX page.

RxJava is Lightweight

RxJava tries to be very lightweight. It is implemented as a single JAR that is focused on just the Observable abstraction and related higher-order functions. You could implement a composable Future that is similarly unbiased, but Akka Futures for example come tied in with an Actor library and a lot of other stuff.)

RxJava is a Polyglot Implementation

RxJava supports Java 6 or higher and JVM-based languages such as Groovy, Clojure, JRuby, Kotlin and Scala.

RxJava is meant for a more polyglot environment than just Java/Scala, and it is being designed to respect the idioms of each JVM-based language. (This is something we’re still working on.)

RxJava Libraries

The following external libraries can work with RxJava:

• Hystrix latency and fault tolerance bulkheading library.
• Camel RX provides an easy way to reuse any of the Apache Camel components, protocols, transports and data formats with the RxJava API
• rxjava-http-tail allows you to follow logs over HTTP, like tail -f
• mod-rxvertx - Extension for VertX that provides support for Reactive Extensions (RX) using the RxJava library
• rxjava-jdbc - use RxJava with jdbc connections to stream ResultSets and do functional composition of statements
• rtree - immutable in-memory R-tree and R*-tree with RxJava api including backpressure