Java Migration
Covers the full upgrade path from Java 8 through 25, hitting each LTS release with the breaking changes that actually matter. Shows you exactly what APIs got removed (JAXB, Security Manager, Unsafe methods), what dependencies to add, and which JVM flags to throw at module system complaints. The migration workflow is sensible: assess, update build config, fix compilation, test, check runtime warnings. Really shines on the feature adoption sections, like showing you when to switch from ThreadLocal to ScopedValues or how virtual threads change concurrency in Java 21. The quick reference tables are clutch when you just need to know what breaks between versions without reading Oracle's release notes.
- skills.sh installs
- 357
- GitHub stars
- 771
- last updated
- Feb 8, 2026
Install
$ npx -y skills add decebals/claude-code-java --skill java-migration --agent claude-codeInstalls into .claude/skills of the current project.
Files
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
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- Repository
- github.com/decebals/claude-code-java
- Categories
- Documentation, Release Management, Java & JVM
- License
- MIT
- First seen
- Jun 11, 2026
More from decebals/claude-code-java
All 18- Security Audit347
- Performance Smell Detection341
- Test Quality336
- Api Contract Review315
- Maven Dependency Audit308
- Logging Patterns300
- Jpa Patterns297
- Changelog Generator251
- Git Commit249
- Issue Triage240
- Java Code Review1.1K
- Clean Code427
- Concurrency Review384
- Solid Principles384
- Architecture Review374
- Design Patterns372
- Spring Boot Patterns358
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