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Top 23 Java Kotlin Projects
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Project mention: YouTube sued over ads in Premium: YouTube claims "promotions" are not "ads" [video] | news.ycombinator.com | 2026-08-24
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AppSignal
AppSignal knows why the f*#k it crashed. Stop vibe-debugging. Every exception, every backtrace, grouped so you see patterns, not noise.
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android-interview-questions
Your Cheat Sheet For Android Interview - Android Interview Questions and Answers
Outcome School Android Program
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Project mention: Goodbye YAML? My First Month with Pkl (Apple's Configuration Language) | dev.to | 2026-08-16
# .github/workflows/pkl-generate.yml name: Generate and Validate Configs on: [push, pull_request] jobs: pkl-generate: runs-on: ubuntu-latest steps: - uses: actions/checkout@v4 - name: Install Pkl CLI run: | curl -L https://github.com/apple/pkl/releases/latest/download/pkl-linux-amd64 \ -o /usr/local/bin/pkl chmod +x /usr/local/bin/pkl - name: Validate all Pkl configurations run: pkl eval --multiple-file-output /dev/null pkl/**/*.pkl - name: Generate Kubernetes manifests run: | for file in k8s/services/*.pkl; do service=$(basename "$file" .pkl) pkl eval "$file" -f yaml > "k8s/manifests/${service}.yaml" done - name: Commit generated manifests run: | git config user.name "github-actions[bot]" git config user.email "github-actions[bot]@users.noreply.github.com" git add k8s/manifests/ git diff --cached --quiet || git commit -m "chore: regenerate manifests from Pkl" git push
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glide-transformations
An Android transformation library providing a variety of image transformations for Glide.
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SaaSHub
SaaSHub - Software Alternatives and Reviews. SaaSHub helps you find the best software and product alternatives
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The Log4j project uses JUnit for their testing suites — a tool loved for its unit tests in particular. The Log4j codebase contained a mixture of JUnit4 and JUnit5, so their team asked if we could take over the migration they started. We had our scope: we’d focus on testing, and deliver the upgrade to JUnit5. This also meant we didn’t need to fully learn the entire codebase to contribute. If you’ve done a migration, you’ll know it can be time-consuming, so we were excited to take this off the team’s hands. Not only can we contribute to raising the codebase quality even further and strengthening the project, it’s unlikely to be the kind of work that introduces a big bug someone needs to take care of later. Double win!
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Project mention: Java at the Edge: Managing Memory in Serverless and Modern APIs | dev.to | 2026-05-12
Reduce memory-heavy dependencies. Third party libraries are often very resource-hungry. Opt for lightweight lambda-friendly frameworks such as Micronaut or Quarkus.
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Is this reasoning, or measurement? If measurement, push it to a deterministic tool. Sonar, Spotless, Ruff, ESLint, coverage gates, pre-commit hooks, complexity calculators. Write a script if no tool exists. That's how just lint got built, and that's the Unix-philosophy move for agentic coding. Hooks fire on tool calls; CI fires on PRs; pre-commit fires on commit. Pick the cheapest layer that catches the failure and run it there.
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LWJGL
LWJGL is a Java library that enables cross-platform access to popular native APIs useful in the development of graphics (OpenGL, Vulkan, bgfx), audio (OpenAL, Opus), parallel computing (OpenCL, CUDA) and XR (OpenVR, LibOVR, OpenXR) applications.
The lwjgl bindings for this were written by a member of the GTNH modpack team, thereby completing the chain of vanilla->modded->vanilla once more https://github.com/LWJGL/lwjgl3/pull/1033
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ObjectBox Java (Kotlin, Android)
Database for Android and JVM - first and fast, lightweight on-device vector database
ObjectBox. (2024). ObjectBox: On-device vector database. https://objectbox.io
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OpenPDF
OpenPDF is an open-source Java library for creating, editing, rendering, and encrypting PDF documents, as well as generating PDFs from HTML. It is licensed under the LGPL and MPL.
Project mention: Spotlight on pdfly, the Swiss Army knife for PDF files | news.ycombinator.com | 2025-10-13 -
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LeafPic
LeafPic is a fluid, material-designed alternative gallery, it also is ad-free and open source under GPLv3 license. It doesn't miss any of the main features of a stock gallery, and we also have plans to add more useful features. (by UnevenSoftware)
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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).
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Your Push Request Succeeded. The Device Key Is Dead.
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A note from our sponsor - AppSignal
www.appsignal.com | 12 Oct 2026
Index
What are some of the best open-source Kotlin projects in Java? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | SmartTube | 34,785 |
| 2 | GmsCore | 14,824 |
| 3 | android-interview-questions | 12,368 |
| 4 | pkl | 11,541 |
| 5 | Permission Dispatcher | 11,167 |
| 6 | glide-transformations | 9,884 |
| 7 | Suwayomi-Server | 7,833 |
| 8 | REST Assured | 7,141 |
| 9 | junit-framework | 7,055 |
| 10 | Micronaut | 6,432 |
| 11 | from-java-to-kotlin | 6,324 |
| 12 | spotless | 5,685 |
| 13 | Blurry | 5,655 |
| 14 | LWJGL | 5,469 |
| 15 | dialogplus | 4,962 |
| 16 | Android Tips & Tricks | 4,748 |
| 17 | ObjectBox Java (Kotlin, Android) | 4,627 |
| 18 | JaCoCo | 4,608 |
| 19 | OpenPDF | 4,375 |
| 20 | springdoc-openapi | 3,736 |
| 21 | vertx-examples | 3,576 |
| 22 | AutoDispose | 3,343 |
| 23 | LeafPic | 3,266 |
Sponsored
AppSignal knows why the f*#k it crashed.
Stop vibe-debugging. Every exception, every backtrace, grouped so you see patterns, not noise.
www.appsignal.com