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reactivex/rxjava

📈 Trending★ 48,252JavaAudience · developerComplexity · 3/5ActiveLicenseSetup · easy

TLDR

A Java library for handling sequences of asynchronous events (like network responses or user input) by chaining operators instead of writing callback-heavy code.

Mindmap

mindmap
  root((RxJava))
    What it does
      Handles async events
      Chains transformations
      Manages threading
    Core types
      Flowable with backpressure
      Observable for UI events
      Single, Maybe, Completable
    Use cases
      Android UI updates
      Server request handling
      Real-time data streams
    Tech stack
      Java
      JVM
      Gradle or Maven
    Benefits
      Avoids callback hell
      Declarative syntax
      Automatic scheduling

Things people build with this

USE CASE 1

Build Android apps that update the UI while handling background network calls without blocking the main thread.

USE CASE 2

Process multiple concurrent server requests by combining and transforming data streams declaratively.

USE CASE 3

Coordinate real-time data from multiple sources (sensors, APIs, user input) into a single reactive pipeline.

USE CASE 4

Replace nested callbacks with readable chains of operators to handle complex asynchronous workflows.

Tech stack

JavaJVMGradleMaven

Getting it running

Difficulty · easy Time to first run · 5min
Use freely for any purpose, including commercial use, as long as you keep the copyright notice.

In plain English

RxJava is a Java library that makes it easier to write programs that deal with sequences of asynchronous events, things like network responses, user input, or real-time data streams, without tangling your code in callbacks, threads, and manual synchronization. The core idea is the observable pattern extended to streams. Instead of calling a function and waiting for a single answer, you subscribe to a source that can emit zero, one, or many items over time. You then chain operators (like map, filter, or merge) to transform or combine those streams declaratively, similar to how you chain operations in SQL or array methods in JavaScript. The library handles threading and scheduling behind the scenes. RxJava provides several base types for different situations. A Flowable supports a potentially unlimited stream with backpressure, meaning it can slow down the producer if a consumer can't keep up, preventing memory overflow. An Observable is similar but without backpressure control, suitable for UI events or short sequences. Single, Maybe, and Completable handle the cases where you expect exactly one result, zero or one result, or just a success/failure signal with no data. The library is particularly useful in Android development (where UI updates must happen on the main thread while network calls happen in the background), server-side Java applications processing many concurrent requests, or any system where you need to coordinate multiple asynchronous data sources. It eliminates the \"callback hell\" problem and makes complex async flows readable as a chain of steps. Built in Java and available on the JVM, RxJava integrates with Gradle or Maven as a single dependency with no required third-party runtime libraries. Version 4 targets modern Java and adds support for virtual threads, which are lightweight concurrency units introduced in recent Java versions.

Copy-paste prompts

Prompt 1
Show me how to use RxJava Flowable to fetch data from an API and update a UI element without blocking the main thread.
Prompt 2
How do I merge multiple RxJava Observables and filter the results based on a condition?
Prompt 3
Give me an example of using RxJava Single to handle a one-time async operation like a login request.
Prompt 4
How do I implement backpressure in RxJava to prevent memory overflow when a producer emits faster than a consumer can process?
Prompt 5
Show me how to chain RxJava operators (map, filter, flatMap) to transform a stream of user input events.
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