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Top 23 Java HacktoberFest Projects
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termux-app
Termux - a terminal emulator application for Android OS extendible by variety of packages.
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Project mention: Top Open-Source Data Engineering Tools- Unravelling the Best in 2026 | dev.to | 2025-12-10
Kestra
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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)
To be fair I've never used Laravel - but I do have a memory of code generators/scaffolders inserting files that made clear they were responsible for work
/*
* NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
* Do not edit the class manually.
*/
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Project mention: AI Alert Assistant: How n8n + LLM Replace Routine Diagnostics | dev.to | 2026-03-23
Personally, it reminds me of Jenkins about ten years ago — and Jenkins was great. You can install n8n using any of the methods described in the documentation, for example using docker-compose
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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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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."
Even worse, 95 (60%) of those pull requests were merged into the main branch, 50 of them by a bot user, without any user interaction. This led to the malicious package being pushed to production code in less than an hour, as showcased by the jhipster/generator-jhipster repository.
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Project mention: Standing on shoulders: the stack that makes Floci start in ~24ms | dev.to | 2026-05-21
Quarkus does at compile time what traditional frameworks do at runtime: bean discovery, dependency injection wiring, configuration resolution, JAX-RS route registration, Jackson serializer generation. That matters because GraalVM is a closed-world compiler. It has to know at compile time every class that might be loaded and every method that might be called via reflection. Quarkus is engineered from the ground up to give the native compiler that information.
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bytecode-viewer
A Java 8+ Jar & Android APK Reverse Engineering Suite (Decompiler, Editor, Debugger & More)
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Project mention: I built an open-source CLI that scores any site for AI-agent readiness (0-100) | dev.to | 2026-05-07
It does not check for vulnerabilities — use OWASP ZAP for that.
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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: Turning Google Search into a Kafka Event Stream for Many Consumers | dev.to | 2026-02-03
Next, Kafka requires Zookeeper and a broker. Instead of installing them manually, we use Docker Compose with this YAML file.
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GitHub: https://github.com/provectus/kafka-ui
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Apache Iceberg 1.11 has been released (I even got some small contributions merged 🎉). There are more details of the release in these blog posts:
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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.
Added guard rails: Added unit and integration tests, added auto code formatting with spotless, added code analysis using checkstyle
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The Spring AI reference provides plenty of guidance and recommendations around MCP as well as other parts of Genative AI such as using chat clients or RAG.
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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.
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Project mention: I've been curating FOSS & privacy apps on Telegram for 8 months. Here's how I do it. | dev.to | 2026-04-27
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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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Standing on shoulders: the stack that makes Floci start in ~24ms
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Rendering powerpoint to png files with JBang
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I've been curating FOSS & privacy apps on Telegram for 8 months. Here's how I do it.
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Next-Level Observability with OpenTelemetry
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Weather MCP
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iceberg VS sail - a user suggested alternative
2 projects | 18 Mar 2026 -
YouTube as Storage
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A note from our sponsor - SaaSHub
www.saashub.com | 14 Jun 2026
Index
What are some of the best open-source HacktoberFest projects in Java? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | Design Patterns | 94,119 |
| 2 | Java | 65,829 |
| 3 | termux-app | 56,336 |
| 4 | kestra | 27,048 |
| 5 | openapi-generator | 26,395 |
| 6 | Jenkins | 25,418 |
| 7 | Apache RocketMQ | 22,453 |
| 8 | JHipster | 22,419 |
| 9 | Quarkus | 15,721 |
| 10 | bytecode-viewer | 15,532 |
| 11 | ZAP | 15,277 |
| 12 | SuperTokens Community | 15,083 |
| 13 | Apache ZooKeeper | 12,763 |
| 14 | kafka-ui | 12,055 |
| 15 | jjwt | 11,083 |
| 16 | android-gif-drawable | 9,647 |
| 17 | iceberg | 8,957 |
| 18 | Checkstyle | 8,947 |
| 19 | spring-ai | 8,926 |
| 20 | Testcontainers | 8,658 |
| 21 | graylog | 8,061 |
| 22 | AntennaPod | 7,928 |
| 23 | CompreFace | 7,862 |
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