Ghidra is a software reverse engineering (SRE) framework

Dex to Java decompiler

RxJava – Reactive Extensions for the JVM – a library for composing asynchronous and event-based programs using observable sequences for the Java VM.

A libre lightweight streaming front-end for Android.

Bind Android views and callbacks to fields and methods.

Desktop/Android/HTML5/iOS Java game development framework

Event bus for Android and Java that simplifies communication between Activities, Fragments, Threads, Services, etc. Less code, better quality.

JDK main-line development https://openjdk.org/projects/jdk

This project is deprecated and stale. The latest ExoPlayer code is available in https://github.com/androidx/media

High Performance Inter-Thread Messaging Library

A fast dependency injector for Android and Java.

QuestDB is a high performance, open-source, time-series database

Modern Java - A Guide to Java 8

A Java 8+ Jar & Android APK Reverse Engineering Suite (Decompiler, Editor, Debugger & More)

A standalone Java Decompiler GUI

Stetho is a debug bridge for Android applications, enabling the powerful Chrome Developer Tools and much more.

A declarative API to handle Android runtime permissions.

A barebones WebSocket client and server implementation written in 100% Java.

Paging indicator widgets compatible with the ViewPager from the Android Support Library and ActionBarSherlock.

Efficient reliable UDP unicast, UDP multicast, and IPC message transport

A damn simple library for building production-ready RESTful web services.

Java interface to OpenCV, FFmpeg, and more

Android library (AAR). Highly configurable, easily extendable deep zoom view for displaying huge images without loss of detail. Perfect for photo galleries, maps, building plans etc.

Android application powering the mirror in my house

Asynchronous socket, http(s) (client+server) and websocket library for android. Based on nio, not threads.

OWASP dependency-check is a software composition analysis utility that detects publicly disclosed vulnerabilities in application dependencies.

Tiny, easily embeddable HTTP server in Java.

A RecyclerView(advanced and flexible version of ListView in Android) with refreshing,loading more,animation and many other features.

A custom ViewPager title strip which gives continuous feedback to the user when scrolling

Runtime code generation for the Java virtual machine.