ReactiveX/RxJava

Maintainer? Show your league in your README

Card: your league's emblem, from Copper to Legendary

[![bestofgithub](https://bestofgithub.dev/badge/ReactiveX/RxJava.svg?style=card)](https://bestofgithub.dev/repo/ReactiveX/RxJava)

Flat: fits beside your other badges

[![bestofgithub](https://bestofgithub.dev/badge/ReactiveX/RxJava.svg)](https://bestofgithub.dev/repo/ReactiveX/RxJava)

Loading README…

	Flowable	Observable	Single	Maybe	Completable	Streamable
Flowable		`toObservable`	`first`, `firstOrError`, `single`, `singleOrError`, `last`, `lastOrError`¹	`firstElement`, `singleElement`, `lastElement`	`ignoreElements`	`toStreamable`
Observable	`toFlowable`²		`first`, `firstOrError`, `single`, `singleOrError`, `last`, `lastOrError`¹	`firstElement`, `singleElement`, `lastElement`	`ignoreElements`	`toStreamable`
Single	`toFlowable`³	`toObservable`		`toMaybe`	`ignoreElement`	`toStreamable`
Maybe	`toFlowable`³	`toObservable`	`toSingle`		`ignoreElement`	`toStreamable`
Completable	`toFlowable`	`toObservable`	`toSingle`	`toMaybe`		`toStreamable`
Streamable	`toFlowable`	`toObservable`	TBD	TBD	TBD

Operator	Overloads
`flatMap`	`flatMapSingle`, `flatMapMaybe`, `flatMapCompletable`, `flatMapIterable`
`concatMap`	`concatMapSingle`, `concatMapMaybe`, `concatMapCompletable`, `concatMapIterable`
`switchMap`	`switchMapSingle`, `switchMapMaybe`, `switchMapCompletable`

Type	Class	Interface	Consumer
0..N backpressured	`Flowable`	`Flow.Publisher`¹	`Flow.Subscriber`
0..N unbounded	`Observable`	`ObservableSource`²	`Observer`
1 element or error	`Single`	`SingleSource`	`SingleObserver`
0..1 element or error	`Maybe`	`MaybeSource`	`MaybeObserver`
0 element or error	`Completable`	`CompletableSource`	`CompletableObserver`
0..N coordinated	`Streamable`	³	`Streamer`, `StreamSink`

RxJava: Reactive Extensions for the JVM

ℹ️ 4.0.0 release: 2026.11.30. Monday. Track

Version 4.x (Javadoc)

Getting started

Setting up the dependency

Hello World

Base classes

Some terminology

Upstream, downstream

Objects in motion

Backpressure

Assembly time

Subscription time

Runtime

Simple background computation

Schedulers

Concurrency within a flow

Parallel processing

Dependent sub-flows

Continuations

Dependent

Non-dependent

Deferred-dependent

Type conversions

Converting to the desired type

Using an overload with the desired type

Operator naming conventions

Unusable keywords

Type erasure

Type ambiguities

Error handling

Base class vs base type

R8 and ProGuard settings

Further reading

Communication

Versioning

@Beta

@Experimental

@Deprecated

io.reactivex.rxjava4.internal.*

Full Documentation

Binaries

Snapshots

Build

Bugs and Feedback

Prior versions

Version 3.x (Javadoc)

Version 2.x

Version 1.x

LICENSE