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Top 23 Java Open-Source Projects

  • GitHub repo JavaGuide

    「Java学习+面试指南」一份涵盖大部分 Java 程序员所需要掌握的核心知识。准备 Java 面试,首选 JavaGuide!

  • GitHub repo Design Patterns

    Design patterns implemented in Java

    Project mention: Next steps? | reddit.com/r/learnjava | 2021-10-04

    Then to Design Patterns. Only a quick introduction: Java Design Patterns

  • Scout APM

    Scout APM: A developer's best friend. Try free for 14-days. Scout APM uses tracing logic that ties bottlenecks to source code so you know the exact line of code causing performance issues and can get back to building a great product faster.

  • GitHub repo advanced-java

    😮 Core Interview Questions & Answers For Experienced Java(Backend) Developers | 互联网 Java 工程师进阶知识完全扫盲:涵盖高并发、分布式、高可用、微服务、海量数据处理等领域知识

  • GitHub repo Spring Boot

    Spring Boot

    Project mention: Learning Resources | reddit.com/r/learnjava | 2021-10-14
  • GitHub repo Elasticsearch

    Free and Open, Distributed, RESTful Search Engine

    Project mention: What is ClickHouse how it compares to PostgreSQL and TimescaleDB for time series | news.ycombinator.com | 2021-10-21

    One thing I was surprised to see is that ClickHouse and ElasticSearch have the same number of contributors. That's pretty astounding given how much older and more prominent ElasticSearch has been.

    https://github.com/ClickHouse/ClickHouse/graphs/contributors

    https://github.com/elastic/elasticsearch/graphs/contributors

  • GitHub repo interviews

    Everything you need to know to get the job. (by kdn251)

    Project mention: Free Computer Science Resources with Interview Prep and much more... | dev.to | 2021-03-29

    11.Interviews

  • GitHub repo RxJava

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

    Project mention: Crash on update | reddit.com/r/NewPipe | 2021-10-14

    ``` io.reactivex.rxjava3.exceptions.OnErrorNotImplementedException: The exception was not handled due to missing onError handler in the subscribe() method call. Further reading: https://github.com/ReactiveX/RxJava/wiki/Error-Handling | java.lang.IllegalStateException: Migration didn't properly handle: feed_group(org.schabi.newpipe.database.feed.model.FeedGroupEntity). Expected: TableInfo{name='feed_group', columns={name=Column{name='name', type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0, defaultValue='null'}, uid=Column{name='uid', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=1, defaultValue='null'}, icon_id=Column{name='icon_id', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}, sort_order=Column{name='sort_order', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}}, foreignKeys=[], indices=[Index{name='index_feed_group_sort_order', unique=false, columns=[sort_order]}]} Found: TableInfo{name='feed_group', columns={uid=Column{name='uid', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=1, defaultValue='null'}, name=Column{name='name', type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0, defaultValue='null'}, icon_id=Column{name='icon_id', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}, sort_order=Column{name='sort_order', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='0'}}, foreignKeys=[], indices=[]} at io.reactivex.rxjava3.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:717) at io.reactivex.rxjava3.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:714) at io.reactivex.rxjava3.internal.subscribers.LambdaSubscriber.onError(LambdaSubscriber.java:79) at io.reactivex.rxjava3.internal.operators.flowable.FlowableObserveOn$BaseObserveOnSubscriber.checkTerminated(FlowableObserveOn.java:209) at io.reactivex.rxjava3.internal.operators.flowable.FlowableObserveOn$ObserveOnSubscriber.runAsync(FlowableObserveOn.java:394) at io.reactivex.rxjava3.internal.operators.flowable.FlowableObserveOn$BaseObserveOnSubscriber.run(FlowableObserveOn.java:176) at io.reactivex.rxjava3.android.schedulers.HandlerScheduler$ScheduledRunnable.run(HandlerScheduler.java:123) at android.os.Handler.handleCallback(Handler.java:938) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:223) at android.app.ActivityThread.main(ActivityThread.java:7665) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:594) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) Caused by: java.lang.IllegalStateException: Migration didn't properly handle: feed_group(org.schabi.newpipe.database.feed.model.FeedGroupEntity). Expected: TableInfo{name='feed_group', columns={name=Column{name='name', type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0, defaultValue='null'}, uid=Column{name='uid', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=1, defaultValue='null'}, icon_id=Column{name='icon_id', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}, sort_order=Column{name='sort_order', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}}, foreignKeys=[], indices=[Index{name='index_feed_group_sort_order', unique=false, columns=[sort_order]}]} Found: TableInfo{name='feed_group', columns={uid=Column{name='uid', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=1, defaultValue='null'}, name=Column{name='name', type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0, defaultValue='null'}, icon_id=Column{name='icon_id', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='null'}, sort_order=Column{name='sort_order', type='INTEGER', affinity='3', notNull=true, primaryKeyPosition=0, defaultValue='0'}}, foreignKeys=[], indices=[]} at androidx.room.RoomOpenHelper.onUpgrade(RoomOpenHelper.java:103) at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.onUpgrade(FrameworkSQLiteOpenHelper.java:177) at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:416) at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:316) at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.getWritableSupportDatabase(FrameworkSQLiteOpenHelper.java:145) at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper.getWritableDatabase(FrameworkSQLiteOpenHelper.java:106) at androidx.room.RoomDatabase.inTransaction(RoomDatabase.java:622) at androidx.room.RoomDatabase.assertNotSuspendingTransaction(RoomDatabase.java:399) at androidx.room.RoomDatabase.query(RoomDatabase.java:442) at androidx.room.util.DBUtil.query(DBUtil.java:83) at org.schabi.newpipe.database.feed.dao.FeedDAO_Impl$7.call(FeedDAO_Impl.java:285) at org.schabi.newpipe.database.feed.dao.FeedDAO_Impl$7.call(FeedDAO_Impl.java:282) at io.reactivex.rxjava3.internal.operators.maybe.MaybeFromCallable.subscribeActual(MaybeFromCallable.java:47) at io.reactivex.rxjava3.core.Maybe.subscribe(Maybe.java:5330) at io.reactivex.rxjava3.internal.operators.flowable.FlowableFlatMapMaybe$FlatMapMaybeSubscriber.onNext(FlowableFlatMapMaybe.java:131) at io.reactivex.rxjava3.internal.operators.flowable.FlowableObserveOn$ObserveOnSubscriber.runAsync(FlowableObserveOn.java:402) at io.reactivex.rxjava3.internal.operators.flowable.FlowableObserveOn$BaseObserveOnSubscriber.run(FlowableObserveOn.java:176) at io.reactivex.rxjava3.internal.schedulers.ExecutorScheduler$ExecutorWorker$BooleanRunnable.run(ExecutorScheduler.java:322) at io.reactivex.rxjava3.internal.schedulers.ExecutorScheduler$ExecutorWorker.runEager(ExecutorScheduler.java:287) at io.reactivex.rxjava3.internal.schedulers.ExecutorScheduler$ExecutorWorker.run(ExecutorScheduler.java:248) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) at java.lang.Thread.run(Thread.java:923)

  • Nanos

    Run Linux Software Faster and Safer than Linux with Unikernels.

  • GitHub repo Guava

    Google core libraries for Java

    Project mention: Guava Idea Graveyard | news.ycombinator.com | 2021-09-17
  • GitHub repo Java

    All Algorithms implemented in Java

    Project mention: GitHub - TheAlgorithms/Java: All Algorithms implemented in Java | reddit.com/r/coding | 2021-07-24
  • GitHub repo OkHttp

    Square’s meticulous HTTP client for the JVM, Android, and GraalVM.

    Project mention: What am I missing? Using Volley, trying to import its classes | reddit.com/r/androiddev | 2021-10-22

    Just some advice, would recommend against volley, it's way more of a pain to use than it needs to be. Instead use okhhtp or retrofit if you want a nice abstraction on top of okhhtp.

  • GitHub repo Retrofit

    A type-safe HTTP client for Android and the JVM

    Project mention: What am I missing? Using Volley, trying to import its classes | reddit.com/r/androiddev | 2021-10-22

    Just some advice, would recommend against volley, it's way more of a pain to use than it needs to be. Instead use okhhtp or retrofit if you want a nice abstraction on top of okhhtp.

  • GitHub repo MPAndroidChart

    A powerful 🚀 Android chart view / graph view library, supporting line- bar- pie- radar- bubble- and candlestick charts as well as scaling, panning and animations.

    Project mention: how can i make this chart? xml&java | reddit.com/r/androiddev | 2021-10-15

    There is no easy way of implementing this. You'll have to use a library like MPAndroidChart

  • GitHub repo Apache Spark

    Apache Spark - A unified analytics engine for large-scale data processing

    Project mention: What is B2D Sector? | dev.to | 2021-10-17

    Example tools:\ Tensorflow, Tableau, Apache Spark, Matlab, Jupyter

  • GitHub repo ZXing

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

    Project mention: Mechanical sympathy for QR codes: making NSW check-in better | news.ycombinator.com | 2021-10-12

    Since most government software is written in Java, the QR codes on PDF check-in posters are probably being generated with ZXing [1].

    [1] https://github.com/zxing/zxing

  • GitHub repo Arthas

    Alibaba Java Diagnostic Tool Arthas/Alibaba Java诊断利器Arthas

    Project mention: Alibaba Summer of Code 2020 – Arthas Final Report | dev.to | 2021-10-19

    Issue

  • GitHub repo jadx

    Dex to Java decompiler

    Project mention: I wrote an open source mod of an Android App | dev.to | 2021-10-04

    But before we take a dive into the smali code, let's look at some good ol' Java code. Android byte-code is an optimized form of Java byte-code, which is very easily and reliably decompilable. Don't get me wrong, the result will contain lots of issues and won't be compilable. The tool of choice for Android decompilation is called JADX. Just hand it an apk file and it will produce an entire Android Studio project for you:

  • GitHub repo leakcanary

    A memory leak detection library for Android.

    Project mention: 25 Best Android Libraries, Projects, and Tools You Won’t Want to Miss Out in 2021 | dev.to | 2021-10-09

    Knowing when root views are detached, e.g. to detect if they might be leaking (LeakCanary).

  • GitHub repo fastjson

    A fast JSON parser/generator for Java.

    Project mention: Ask HN: Differences in Programming Style by Nationalities | news.ycombinator.com | 2021-04-19

    I first noticed a difference in national styles when I contributed a patch to fastjson, a JSON parser in Java from Alibaba.

    Take a look around the repo; it'll look odd to a western programmer. There is a lot of duplication. And the tests don't have names, they are numbered.

    https://github.com/alibaba/fastjson/blob/master/src/test/jav...

    This was several years ago. I did end up choosing it since it really was the fastest.

  • GitHub repo spring-boot-demo

    该项目已成功集成 actuator(监控)、admin(可视化监控)、logback(日志)、aopLog(通过AOP记录web请求日志)、统一异常处理(json级别和页面级别)、freemarker(模板引擎)、thymeleaf(模板引擎)、Beetl(模板引擎)、Enjoy(模板引擎)、JdbcTemplate(通用JDBC操作数据库)、JPA(强大的ORM框架)、mybatis(强大的ORM框架)、通用Mapper(快速操作Mybatis)、PageHelper(通用的Mybatis分页插件)、mybatis-plus(快速操作Mybatis)、BeetlSQL(强大的ORM框架)、upload(本地文件上传和七牛云文件上传)、redis(缓存)、ehcache(缓存)、email(发送各种类型邮件)、task(基础定时任务)、quartz(动态管理定时任务)、xxl-job(分布式定时任务)、swagger(API接口管理测试)、security(基于RBAC的动态权限认证)、SpringSession(Session共享)、Zookeeper(结合AOP实现分布式锁)、Ra

  • GitHub repo dbeaver

    Free universal database tool and SQL client

    Project mention: How to Change Another User's Password? | reddit.com/r/dbeaver | 2021-10-06
  • GitHub repo Selenium WebDriver

    A browser automation framework and ecosystem.

    Project mention: After Almost 3 Years Of Development, Selenium v4.0.0 Was Finally Released | news.ycombinator.com | 2021-10-13
  • GitHub repo easyexcel

    快速、简单避免OOM的java处理Excel工具

    Project mention: Any good alternatives to Apache POI for creating Excel spreadsheets? | reddit.com/r/java | 2021-07-03
  • GitHub repo libGDX

    Desktop/Android/HTML5/iOS Java game development framework

    Project mention: LibGDX LWJGL Question! | reddit.com/r/libgdx | 2021-10-20
NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020). The latest post mention was on 2021-10-22.

Index

What are some of the best open-source Java projects? This list will help you:

Project Stars
1 JavaGuide 112,470
2 Design Patterns 70,632
3 advanced-java 58,123
4 Spring Boot 57,723
5 Elasticsearch 56,910
6 interviews 54,243
7 RxJava 45,405
8 Guava 42,666
9 Java 41,587
10 OkHttp 41,003
11 Retrofit 38,876
12 MPAndroidChart 34,102
13 Apache Spark 31,120
14 ZXing 28,536
15 Arthas 27,441
16 jadx 27,438
17 leakcanary 26,837
18 fastjson 23,838
19 spring-boot-demo 23,692
20 dbeaver 22,693
21 Selenium WebDriver 21,877
22 easyexcel 21,481
23 libGDX 19,093
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