1) RxJava: Reactive Extensions for the JVM
RxJava is a Java VM implementation of Reactive Extensions, which is a library for composing asynchronous and event-based programs by using observable sequences.
GitHub Stars: 33k+
The GitHub page of RxJava from where you can download and see the project code is:
https://github.com/ReactiveX/RxJava#rxjava-reactive-extensions-for-the-jvm
2) Elasticsearch
Elasticsearch is a distributed RESTful search engine built for the cloud.
GitHub Stars: 31k+
The GitHub page of Elasticsearch from where you can download and see the project code is:
https://github.com/elastic/elasticsearch
3) Retrofit
Type-safe HTTP client for Android and Java by Square, Inc.
GitHub Stars: 28k+
The GitHub page of Retrofit from where you can download and see the project code is:
https://github.com/square/retrofit
4) OkHttp
An HTTP & HTTP/2 client for Android and Java applications.
GitHub Stars: 27k+
The GitHub page of OkHttp from where you can download and see the project code is:
https://github.com/square/okhttp
5) Spring Boot
Spring Boot makes it easy to create Spring-powered, production-grade applications and services with absolute minimum fuss. It takes an opinionated view of the Spring platform so that new and existing users can quickly get to the bits they need.
GitHub Stars: 25k+
The GitHub page of Spring Boot from where you can download and see the project code is:
https://github.com/spring-projects/spring-boot
6) Guava: Google Core Libraries for Java
Guava is a set of core libraries that includes new collection types (such as multimap and multiset), immutable collections, a graph library, functional types, an in-memory cache, and APIs/utilities for concurrency, I/O, hashing, primitives, reflection, string processing, and much more!
GitHub Stars: 24.5k+
The GitHub page of Guava from where you can download and see the project code is:
https://github.com/google/guava
7) MPAndroidChart
A powerful & easy to use chart library for Android
GitHub Stars: 22.5k+
The GitHub page of MPAndroidChart from where you can download and see the project code is:
https://github.com/PhilJay/MPAndroidChart
8) Glide
Glide is a fast and efficient open source media management and image loading framework for Android that wraps media decoding, memory and disk caching, and resource pooling into a simple and easy to use interface.
GitHub Stars: 22k+
The GitHub page of Glide from where you can download and see the project code is:
https://github.com/bumptech/glide
9) Spring Framework
Spring provides everything you need beyond the Java language to create enterprise applications in a wide range of scenarios and architectures.
GitHub Stars: 21.5k+
The GitHub page of Spring Framework from where you can download and see the project code is:
https://github.com/spring-projects/spring-framework
10) Butter Knife
Field and method binding for Android views which uses annotation processing to generate boilerplate code for you.
GitHub Stars: 21k+
The GitHub page of Butter Knife from where you can download and see the project code is:
https://github.com/JakeWharton/butterknife
11) Lottie for Android
Lottie is a mobile library for Android and iOS that parses Adobe After Effects animations exported as json with Bodymovin and renders them natively on mobile!
GitHub Stars: 21k+
The GitHub page of Lottie from where you can download and see the project code is:
https://github.com/airbnb/lottie-android
12) LeakCanary
A memory leak detection library for Android and Java.
GitHub Stars: 19.5k+
The GitHub page of LeakCanary from where you can download and see the project code is:
https://github.com/square/leakcanary
13) Apache Dubbo
Apache Dubbo (incubating) is a high-performance, java based RPC framework open-sourced by Alibaba.
GitHub Stars: 19k+
The GitHub page of Apache Dubbo from where you can download and see the project code is:
https://github.com/apache/incubator-dubbo
14) ZXing
ZXing (?zebra crossing?) is an open-source, multi-format 1D/2D barcode image processing library implemented in Java, with ports to other languages.
GitHub Stars: 18.5k+
The GitHub page of ZXing from where you can download and see the project code is:
https://github.com/zxing/zxing
15) EventBus
EventBus is a publish/subscribe event bus for Android and Java.
GitHub Stars: 18k+
The GitHub page of EventBus from where you can download and see the project code is:
https://github.com/greenrobot/EventBus
16) AndroidUtilCode
AndroidUtilCode is a powerful & easy to use library for Android. This library encapsulates the functions that commonly used in Android development which have complete demo and unit test. By using it?s encapsulated APIs, you can greatly improve the development efficiency. The program mainly consists of two modules which is utilcode, which is commonly used in development, and subutil which is rarely used in development, but the utils can be beneficial to simplify the main module.
GitHub Stars: 18k+
The GitHub page of AndroidUtilCode from where you can download and see the project code is:
https://github.com/Blankj/AndroidUtilCode
17) Universal Image Loader
UIL aims to provide a powerful, flexible and highly customizable instrument for image loading, caching and displaying. It provides a lot of configuration options and good control over the image loading and caching process.
GitHub Stars: 16k+
The GitHub page of Universal Image Loader from where you can download and see the project code is:
https://github.com/nostra13/Android-Universal-Image-Loader
18) Picasso
A powerful image downloading and caching library for Android (Java).
GitHub Stars: 15.5k+
The GitHub page of Picasso from where you can download and see the project code is:
https://github.com/square/picasso
19) JADX
Command line and GUI tools for produce Java source code from Android Dex and Apk files.
GitHub Stars: 14.9k+
The GitHub page of JADX from where you can download and see the project code is:
https://github.com/skylot/jadx
20) Fresco
Fresco is a powerful system for displaying images in Android applications.
GitHub Stars: 14.5k+
The GitHub page of Fresco from where you can download and see the project code is:
https://github.com/facebook/fresco
21) Netty
Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients.
GitHub Stars: 14k+
The GitHub page of Netty from where you can download and see the project code is:
https://github.com/netty/netty
22) libGDX
libGDX is a cross-platform Java game development framework based on OpenGL (ES) that works on Windows, Linux, Mac OS X, Android, your WebGL enabled browser and iOS.
GitHub Stars: 13.9k+
The GitHub page of libGDX from where you can download and see the project code is:
https://github.com/libgdx/libgdx
23) Hystrix
Hystrix is a latency and fault tolerance library designed to isolate points of access to remote systems, services and 3rd party libraries, stop cascading failure and enable resilience in complex distributed systems where failure is inevitable.
GitHub Stars: 13.9k+
The GitHub page of Hystrix from where you can download and see the project code is:
https://github.com/Netflix/Hystrix
24) Fastjson
Fastjson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Fastjson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of.
GitHub Stars: 13.8k+
The GitHub page of Fastjson from where you can download and see the project code is:
https://github.com/alibaba/fastjson
25) BRVAH
Powerful and flexible RecyclerAdapter,
GitHub Stars: 13.8k+
The GitHub page of BRVAH from where you can download and see the project code is:
https://github.com/CymChad/BaseRecyclerViewAdapterHelper
26) Material Dialogs
A beautiful, fluid, and customizable dialogs API.
GitHub Stars: 13.5k+
The GitHub page of Material Dialogs from where you can download and see the project code is:
https://github.com/afollestad/material-dialogs
27) PhotoView
PhotoView aims to help produce an easily usable implementation of a zooming Android ImageView.
GitHub Stars: 13k+
The GitHub page of PhotoView from where you can download and see the project code is:
https://github.com/chrisbanes/PhotoView
28) Tinker
Tinker is a hot-fix solution library for Android, it supports dex, library and resources update without reinstalling apk.
GitHub Stars: 11.9k+
The GitHub page of Tinker from where you can download and see the project code is:
https://github.com/Tencent/tinker
29) Material-Animations
Android Transition animations explanation with examples.
GitHub Stars: 11.6k+
The GitHub page of Material-Animations from where you can download and see the project code is:
https://github.com/lgvalle/Material-Animations
30) Plaid
An Android (Java) app which provides design news and inspiration as well as being an example of implementing material design.
GitHub Stars: 11k+
The GitHub page of Plaid from where you can download and see the project code is:
https://github.com/nickbutcher/plaid
31) SlidingMenu
An Android (Java) library that allows you to easily create applications with slide-in menus.
GitHub Stars: 11k+
The GitHub page of SlidingMenu from where you can download and see the project code is:
https://github.com/jfeinstein10/SlidingMenu
32) Jenkins
Jenkins is the leading open-source automation server. Built with Java, it provides over 1000 plugins to support automating virtually anything, so that humans can actually spend their time doing things machines cannot.
GitHub Stars: 10k+
The GitHub page of Jenkins from where you can download and see the project code is:
https://github.com/jenkinsci/jenkins
33) ExoPlayer
An extensible media player for Android (Java).
GitHub Stars: 10k+
The GitHub page of ExoPlayer from where you can download and see the project code is:
https://github.com/google/ExoPlayer
34) greenDAO
greenDAO is a light & fast ORM solution for Android (Java) that maps objects to SQLite databases.
GitHub Stars: 9.5k+
The GitHub page of greenDAO from where you can download and see the project code is:
https://github.com/greenrobot/greenDAO
35) Realm
Realm is a mobile database that runs directly inside phones, tablets or wearables. This repository holds the source code for the Java version of Realm, which currently runs only on Android.
GitHub Stars: 9.5k+
The GitHub page of Realm from where you can download and see the project code is:
https://github.com/realm/realm-java
36) Logger
Simple, pretty and powerful logger for android (Java).
GitHub Stars: 9k+
The GitHub page of Logger from where you can download and see the project code is:
https://github.com/orhanobut/logger
37) Bazel
A fast, scalable, multi-language and extensible build system.
GitHub Stars: 9k+
The GitHub page of Bazel from where you can download and see the project code is:
https://github.com/bazelbuild/bazel
38) MyBatis
MyBatis SQL mapper framework for Java.
GitHub Stars: 7k+
The GitHub page of MyBatis from where you can download and see the project code is:
https://github.com/mybatis/mybatis-3
39) Dagger
A fast dependency injector for Android and Java by Square.
GitHub Stars: 6.5k+
The GitHub page of Dagger from where you can download and see the project code is:
https://github.com/square/dagger
40) Guice
Guice (pronounced ?juice?) is a lightweight dependency injection framework for Java 6 and above, brought to you by Google.
GitHub Stars: 6.5k+
The GitHub page of Guice from where you can download and see the project code is:
https://github.com/google/guice
41) Auto
A collection of source code generators for Java.
GitHub Stars: 6.5k+
The GitHub page of Auto from where you can download and see the project code is:
https://github.com/google/auto
42) JUnit 4
A programmer-oriented testing framework for Java.
GitHub Stars: 6.5k+
The GitHub page of JUnit 4 from where you can download and see the project code is:
https://github.com/junit-team/junit4
43) Mockito
Popular Mocking framework for unit tests written in Java.
GitHub Stars: 6.5k+
The GitHub page of Mockito from where you can download and see the project code is:
https://github.com/mockito/mockito
44) JavaPoet
A Java API for generating .java source files by Square.
GitHub Stars: 5k+
The GitHub page of JavaPoet from where you can download and see the project code is:
https://github.com/square/javapoet
45) OpenRefine
OpenRefine is a free, open source power tool for working with messy data and improving it. GitHub Stars: 5k+
The GitHub page of OpenRefine from where you can download and see the project code is:
https://github.com/OpenRefine/OpenRefine
46) j2objc
A Java to iOS Objective-C translation tool and runtime by Google.
GitHub Stars: 5k+
The GitHub page of j2objc from where you can download and see the project code is:
https://github.com/google/j2objc
47) Rebound
A Java library that models spring dynamics and adds real world physics to your app by Facebook.
GitHub Stars: 5k+
The GitHub page of Rebound from where you can download and see the project code is:
https://github.com/facebook/rebound
48) ScribeJava
Simple OAuth library for Java.
GitHub Stars: 4k+
The GitHub page of ScribeJava from where you can download and see the project code is:
https://github.com/scribejava/scribejava
49) Moshi
A modern JSON library for Android and Java by Square.
GitHub Stars: 3.9k+
The GitHub page of Moshi from where you can download and see the project code is:
https://github.com/square/moshi
50) Socket.IO-client Java
This is the Socket.IO v1.x Client Library for Java. GitHub Stars: 2.5k+
The GitHub page of Socket.IO-client Java from where you can download and see the project code is:
https://github.com/socketio/socket.io-client-java
I hope you like Top 50 Java libraries? list. That?s it for this article!
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