Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/decebals/claude-code-java/java-migrationnpx skills add decebals/claude-code-java --skill java-migrationgit clone --depth 1 https://github.com/decebals/claude-code-javaWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00051 | $0.03851 |
| Opus 5 | $0.00026 | $0.01925 |
| Sonnet 5 | $0.00010 | $0.00770 |
| Haiku 4.5 | $0.00005 | $0.00385 |
Grade A, and why
java-migration scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 571 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Java Migration Skill
Step-by-step guide for upgrading Java projects between major versions.
When to Use
- User says "upgrade to Java 25" / "migrate from Java 8" / "update Java version"
- Modernizing legacy projects
- Spring Boot 2.x → 3.x → 4.x migration
- Preparing for LTS version adoption
Migration Paths
Java 8 (LTS) → Java 11 (LTS) → Java 17 (LTS) → Java 21 (LTS) → Java 25 (LTS)
│ │ │ │ │
└──────────────┴───────────────┴──────────────┴───────────────┘
Always migrate LTS → LTS
Quick Reference: What Breaks
| From → To | Major Breaking Changes |
|---|---|
| 8 → 11 | Removed javax.xml.bind, module system, internal APIs |
| 11 → 17 | Sealed classes (preview→final), strong encapsulation |
| 17 → 21 | Pattern matching changes, finalize() deprecated for removal |
| 21 → 25 | Security Manager removed, Unsafe methods removed, 32-bit dropped |
Migration Workflow
Step 1: Assess Current State
# Check current Java version
java -version
# Check compiler target in Maven
grep -r "maven.compiler" pom.xml
# Find usage of removed APIs
grep -r "sun\." --include="*.java" src/
grep -r "javax\.xml\.bind" --include="*.java" src/
Step 2: Update Build Configuration
Maven:
<properties>
<java.version>21</java.version>
<maven.compiler.source>${java.version}</maven.compiler.source>
<maven.compiler.target>${java.version}</maven.compiler.target>
</properties>
<!-- Or with compiler plugin -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.12.1</version>
<configuration>
<release>21</release>
</configuration>
</plugin>
Gradle:
java {
toolchain {
languageVersion = JavaLanguageVersion.of(21)
}
}
Step 3: Fix Compilation Errors
Run compile and fix errors iteratively:
mvn clean compile 2>&1 | head -50
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- yesterday First seen · 571 lines · 51 tokens per session scan A a3e398c6d9bc
java-migration is a skill published in the GitHub repository decebals/claude-code-java (722 stars, last pushed 3d ago), licensed MIT. It adds 51 tokens to every session and 3,851 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
autoimplement
Auto-advance a multi-phase plan: dispatch a subagent per phase, chain /review /pitfall-verification at each boundary, stop on actionable findings. Use for "autoimplement", "run this plan end-to-end", "auto-advance phases".
swiftui-design-consultation
Apple-canon design system for SwiftUI projects: produces DESIGN.md + a Swift Package starter (semantic colors, SF Pro, Liquid Glass, motion, accessibility). Use when starting or refreshing a SwiftUI design system.
ios-native-review
After a PRD/spec/plan for an iOS app, before implementation: validate the artifact against Apple HIG (iOS) via WebFetch citations. Asks "is this iOS-native?" — complements pitfall-verification and quality-review.
libgdx-2d-rendering
Use when writing libGDX Java/Kotlin code involving 2D rendering — SpriteBatch, ShapeRenderer, Texture, TextureRegion, TextureAtlas, Camera, Viewport, draw ordering, blending, or screen clearing. Use when debugging rendering artifacts, missing sprites, stretched graphics, or begin/end errors.
libgdx-asset-manager
Use when writing libGDX Java/Kotlin code involving AssetManager — loading assets (Texture, TextureAtlas, Sound, Music, BitmapFont, Skin, Model, TiledMap, ParticleEffect, ShaderProgram, I18NBundle), async loading screens, reference counting, screen transitions, custom loaders, or FreeType font loading via AssetManager.…
libgdx-bitmap-font-text
Use when writing libGDX Java/Kotlin code involving text rendering (BitmapFont, GlyphLayout, BitmapFontCache), NinePatch scalable graphics, DistanceFieldFont, or color markup language. Use when debugging wrong text position, blurry scaled fonts, text measurement, or NinePatch stretching issues.