RxJava

# RxJava: Reactive Extensions for the JVM

## :information_source: 4.0.0 release: 2026.11.30. Monday. [Track](https://github.com/ReactiveX/RxJava/milestone/30)

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RxJava is a Java VM implementation of [Reactive Extensions](http://reactivex.io): a library for composing asynchronous and event-based programs by using observable sequences.

It extends the [observer pattern](http://en.wikipedia.org/wiki/Observer_pattern) to support sequences of data/events and adds operators that allow you to compose sequences together declaratively while abstracting away concerns about things like low-level threading, synchronization, thread-safety and concurrent data structures.

#### Version 4.x ([Javadoc](http://reactivex.io/RxJava/4.x/javadoc/))

- :+1: Native Java 26 implementation<sup>1</sup>.
- :+1: No 3rd party library required at runtime.
- :+1: JPMS and :question: OSGi support still intact.
- :+1: `java.util.concurrent.Flow`-based implementation.
- :+1: Virtual Thread support; `virtualCreate()`, `virtualTransform()`, :eye: `Schedulers.virtual()`.
- :+1: New `Streamable<T>` built around Virtual Threads & virtual blocking. Think `IAsyncEnumerable` for Java. :satellite: in progress.
- :+1: Using Java Cleaner API to detect resource leaks and using it for adaptive cleanups.
- :information_source: Reactive Streams Test Compatibility Kit usage; [Reactive-Streams](https://github.com/reactive-streams/reactive-streams-jvm).
- :satellite: Reduce overload bloat by using `record`-based configurations.
- :satellite: Internal optimizations now that I have the master :key:.
- :eye: Possible usages for Scoped variables for context and per-item resource management.
- :eye: Possible inclusion of 2nd and 3rd party operators.
- :question: Android compatibility depends on your API level and what desugaring is available.
- :warning: RxJava 3.x support will be toned down in the coming months, will be offered for +1 year after 4.x official release.

<sup>1</sup> :stop: Unfortunately Java 27 has no language or API enhancements we can use, because Structured Concurrency remained preview for one.

## Getting started

### Setting up the dependency

The first step is to include RxJava 4 into your project, for example, as a Gradle