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Top 23 Java HacktoberFest Projects
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InfluxDB
InfluxDB – Built for High-Performance Time Series Workloads. InfluxDB 3 OSS is now GA. Transform, enrich, and act on time series data directly in the database. Automate critical tasks and eliminate the need to move data externally. Download now.
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termux-app
Termux - a terminal emulator application for Android OS extendible by variety of packages.
Just go to GitHub releases And download the apk install it We will see configuration steps later the only downside is you need to redownload on each release
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openapi-generator
OpenAPI Generator allows generation of API client libraries (SDK generation), server stubs, documentation and configuration automatically given an OpenAPI Spec (v2, v3)
Project mention: MCP Apps just dropped (OpenAI and Anthropic collab) and I think this is huge | news.ycombinator.com | 2025-11-23 - Project mention: Moving from GitHub Actions? Software binary management for any CI/CD pipeline | dev.to | 2025-12-20
Jenkins is a widely used, time-tested, and open source CI/CD platform which allows full self-hosting. Find the Buildstash plugin in the Jenkins Plugin Index, to upload built binaries from either Freestyle or Pipeline style workflows.
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JHipster
JHipster, much like Spring initializr, is a generator to create a boilerplate backend application, but also with an integrated front end implementation in React, Vue or Angular. In their own words, it "Is a development platform to quickly generate, develop, & deploy modern web applications & microservice architectures."
My first contribution to the jhipster-generator was on 07/2021: https://github.com/jhipster/generator-jhipster/pull/15724. After blogging for a while, I decided to contribute to the JHipster Lite project and wrote about the experience here: https://renanfranca.github.io/how-did-i-earn-money-to-fix-an-issue-from-an-open-source-software.html. Then, I made 10 contributions to the JHipster Lite project (https://github.com/jhipster/jhipster-lite/pulls?q=is%3Apr+author%3A%40me+is%3Aclosed).
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Apache RocketMQ
Apache RocketMQ is a cloud native messaging and streaming platform, making it simple to build event-driven applications.
● Apache RocketMQ: Some capabilities will also be published to the open source community in the next one or two months. https://github.com/apache/rocketmq
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Stream
Stream - Scalable APIs for Chat, Feeds, Moderation, & Video. Stream helps developers build engaging apps that scale to millions with performant and flexible Chat, Feeds, Moderation, and Video APIs and SDKs powered by a global edge network and enterprise-grade infrastructure.
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bytecode-viewer
A Java 8+ Jar & Android APK Reverse Engineering Suite (Decompiler, Editor, Debugger & More)
- Project mention: I Tested 7 Open Source Clerk Alternatives for Full-Stack Developers | dev.to | 2025-11-26
SuperTokens is different. It's built like building blocks.
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- Project mention: Reverse Proxy Deep Dive: The Hidden Complexity of Service Discovery | dev.to | 2025-07-30
ZooKeeper (classic choice for strongly consistent registries). Examples: Pinterest, Linkedin
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Paper
The most widely used, high performance Minecraft server that aims to fix gameplay and mechanics inconsistencies
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GitHub: https://github.com/provectus/kafka-ui
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Checkstyle
Checkstyle is a development tool to help programmers write Java code that adheres to a coding standard. By default it supports the Google Java Style Guide and Sun Code Conventions, but is highly configurable. It can be invoked with an ANT task and a command line program.
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Testcontainers
Testcontainers is a Java library that supports JUnit tests, providing lightweight, throwaway instances of common databases, Selenium web browsers, or anything else that can run in a Docker container.
There are a handful of ways to start Testcontainers, including JUnit4 annotations, JUnit5 annotations, ApplicationContextInitializer, JDBC URL scheme, and manual container lifecycle control. Let's choose manual control for now as the least "magic" option:
- Project mention: Vortex: An extensible, state of the art columnar file format | news.ycombinator.com | 2025-11-14
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🔗 Graylog
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- Project mention: From First Issue to Merged PR: My Journey Contributing to Spring AI | dev.to | 2025-10-19
Pull Request: Fix Azure OpenAI Auto-Configuration – spring-projects/spring-ai#4636
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公式サイト / GitHub：https://wiremock.org
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SaaSHub
SaaSHub - Software Alternatives and Reviews. SaaSHub helps you find the best software and product alternatives
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).
Java HacktoberFest discussion
Java HacktoberFest related posts
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Alternatives to GitHub Actions for self-hosted runners
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How to setup termux on android
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Show HN: Auth0 open-source alternative with self-hosting
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Google will allow users to sideload Android apps without verification
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Hacktoberfest 2025
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Liquibase continues to advertise itself as "open source" despite license switch
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Everything-as-Code explained
- A note from our sponsor - Stream getstream.io | 22 Dec 2025
Index
What are some of the best open-source HacktoberFest projects in Java? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | Design Patterns | 93,516 |
| 2 | Java | 64,536 |
| 3 | termux-app | 47,908 |
| 4 | openapi-generator | 25,434 |
| 5 | Jenkins | 24,794 |
| 6 | JHipster | 22,286 |
| 7 | Apache RocketMQ | 22,244 |
| 8 | Quarkus | 15,357 |
| 9 | bytecode-viewer | 15,348 |
| 10 | SuperTokens Community | 14,778 |
| 11 | ZAP | 14,542 |
| 12 | Apache ZooKeeper | 12,691 |
| 13 | Paper | 11,761 |
| 14 | kafka-ui | 11,501 |
| 15 | jjwt | 10,961 |
| 16 | android-gif-drawable | 9,647 |
| 17 | Checkstyle | 8,769 |
| 18 | Testcontainers | 8,537 |
| 19 | iceberg | 8,343 |
| 20 | graylog | 7,912 |
| 21 | AntennaPod | 7,488 |
| 22 | spring-ai | 7,431 |
| 23 | WireMock | 7,086 |
Sponsored
InfluxDB – Built for High-Performance Time Series Workloads
InfluxDB 3 OSS is now GA. Transform, enrich, and act on time series data directly in the database. Automate critical tasks and eliminate the need to move data externally. Download now.
www.influxdata.com