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JSpecify Nullability Setup Skill

Wires JSpecify, NullAway/ErrorProne and @NullMarked into a Java project so null bugs fail the build.

Dev & CodingIntermediate★ 187⑂ 42AI score 9/10Last updated: Sep 3, 2026

What it does

  • Adds the jspecify dependency plus nullability-maven-plugin for Maven, or ErrorProne + NullAway plugins for Gradle.
  • Creates or updates package-info.java in every src/main/java package with @NullMarked, preserving existing content.
  • Runs scripts/verify_nullmarked.py to confirm no non-empty package was missed.
  • Guides migration from JSR-305/javax, Jakarta, JetBrains, Spring, Android, Checker Framework annotations via the OpenRewrite MigrateToJSpecify recipe.
  • Provides an incremental @NullUnmarked adoption strategy for large/legacy codebases and Kotlin (K2) interop notes.

Who it's for

  • Java developers who want NPEs caught at compile time instead of production.
  • Teams cleaning up a mix of competing nullability annotation libraries.
  • Mixed Java/Kotlin codebases that need accurate nullability across the boundary.

Example uses

  1. "Add JSpecify support to this Gradle project" → plugins, dependencies, and @NullMarked across packages.
  2. "Migrate our javax.annotation.Nullable usages to JSpecify" → OpenRewrite recipe plus manual mappings.
  3. "Turn on null checking gradually, starting with the core module" → OnlyNullMarked mode, package-by-package rollout.

· · · Install guide · · ·

Try it now, no install

Paste this into Claude to use the skill without installing anything.

Read the instructions in this file and follow them to help me:
https://raw.githubusercontent.com/sivaprasadreddy/sivalabs-agent-skills/HEAD/skills/jspecify/SKILL.md

What I want: (describe your task here)

If Claude can't open the link, open it yourself and paste the contents instead.

↓ If it works for you, download the ZIP below and install it. Then it runs on its own — no pasting each time.

Install in the Claude app (no terminal)
  1. Download the ZIP with the button below.
  2. In Claude, open Settings → Capabilities and turn on 'Code execution and file creation'. (one time)
  3. Go to Customize → Skills → + → 'Upload a skill' and upload the ZIP.
↓ Download ZIP
Install in Claude Code

Let Claude do it — paste this into Claude Code

Install the skill I found on Claude Skill Mart.
Copy the skills/jspecify folder from the GitHub repo sivaprasadreddy/sivalabs-agent-skills into my ~/.claude/skills/jspecify-skill/.
When it's done, tell me in one line what this skill can do.

Install with a command instead

git clone https://github.com/sivaprasadreddy/sivalabs-agent-skills.git /tmp/sivalabs-agent-skills && mkdir -p ~/.claude/skills && cp -r /tmp/sivalabs-agent-skills/skills/jspecify ~/.claude/skills/

⚠ This is a third-party skill. Check the source repository before installing.

  1. Open a terminal.
  2. Clone the repo: git clone https://github.com/sivaprasadreddy/sivalabs-agent-skills.git
  3. Create the skills folder: mkdir -p ~/.claude/skills
  4. Copy the skill: cp -r sivalabs-agent-skills/skills/jspecify ~/.claude/skills/
  5. Verify SKILL.md plus the references/ and scripts/ folders were copied.
  6. Restart Claude Code, open your Java project, and ask it to "add JSpecify support".
  7. Install Python 3 if you want the verify_nullmarked.py check to run.
View source on GitHub ↗License: MIT