Ghidra is a software reverse engineering (SRE) framework

Dex to Java decompiler

ZXing ("Zebra Crossing") barcode scanning library for Java, Android

Desktop/Android/HTML5/iOS Java game development framework

FizzBuzz Enterprise Edition is a no-nonsense implementation of FizzBuzz made by serious businessmen for serious business purposes.

GraalVM compiles applications into native executables that start instantly, scale fast, and use fewer compute resources 🚀

An Android library for managing images and the memory they use.

Arduino IDE 1.x

A declarative API to handle Android runtime permissions.

A Java API for generating .java source files.

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

Java Native Access

Modifications to the Minecraft base files to assist in compatibility between mods. New Discord: https://discord.minecraftforge.net/

An Android library supports badge notification like iOS in Samsung, LG, Sony and HTC launchers.

A Java to iOS Objective-C translation tool and runtime.

🚀 A Complete Fast Android Networking Library that also supports HTTP/2 🚀

Install and run GNU/Linux on Android

Thumbnailator - a thumbnail generation library for Java

Open-Source Subscription Billing & Payments Platform

Joda-Time is the widely used replacement for the Java date and time classes prior to Java SE 8.

Compiles Java bytecode to JavaScript, WebAssembly and C

Allows Android apps to interact with BLE beacons

The missing Java distribution of native C++ libraries

Copybara: A tool for transforming and moving code between repositories.

iOS and macOS Decompiler

Custom Android RecyclerViewAdapters that collapse and expand

A cross-platform G-Code sender for GRBL, Smoothieware, TinyG and G2core.

Cross-platform framework for building truly native mobile apps with Java or Kotlin. Write Once Run Anywhere support for iOS, Android, Desktop & Web.

For more info see

BusyBox for Android