Agent-Skills.md

Agent Skills: Java Language Patterns

Modern Java 21+ standards including Records, Pattern Matching, and Virtual Threads. Use when working with Java records, sealed classes, switch expressions, text blocks, Optional, or upgrading from older Java versions. (triggers: **/*.java, pom.xml, build.gradle, record, sealed, switch, var, Optional, stream, VirtualThread, instanceof, text block)

UncategorizedID: hoangnguyen0403/agent-skills-standard/java-language

Repository

hoangnguyen0403/agent-skills-standard
HoangNguyen0403License: Apache-2.0
362103

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pnpm dlx add-skill https://github.com/HoangNguyen0403/agent-skills-standard/tree/HEAD/skills/java/java-language

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skills/java/java-language/SKILL.md

Skill Metadata

Name
java-language
Description
Modern Java 21+ standards including Records, Pattern Matching, and Virtual Threads. Use when working with Java records, sealed classes, switch expressions, text blocks, Optional, or upgrading from older Java versions.

Java Language Patterns

Priority: P0 (CRITICAL)

Implementation Guidelines

  • Records: Use record for immutable DTOs/Value Objects. Records auto-generate equals, hashCode, toString. Avoid Lombok @Data on Pojos.
  • Local Variables: Use var for inferred types. Explicitly type interface variables.
  • Switch: Use Switch Expressions (->) and Pattern Matching over complex if/else chains.
  • Text Blocks: Use "" (Text Blocks) for JSON, SQL, or multi-line strings.
  • Pattern Matching: Use instanceof with pattern binding: if (obj instanceof String s).
  • Sealed Classes: Use sealed interface/class with permits clause for domain-driven restricted hierarchies. Switch expressions then exhaustive switch (compiler-verified).
  • Collections: Use List.of(), Map.of(), and Set.of() for immutable collections.
  • Streams: Use stream() pipelines for functional transformations. Use .toList() (Java 16+).
  • Optional: Utilize Optional<T> for return types. Use .ifPresentOrElse() or .orElseThrow().
  • Virtual Threads: Favor Executors.newVirtualThreadPerTaskExecutor() for I/O-heavy workloads.

Anti-Patterns

  • No Nulls: Return Optional or empty collections; avoid null parameters.
  • No Raw Types: Always use generics; never use raw List or Map.
  • No Old Switch: Use switch expressions (->); avoid fall-through.
  • No Manual get/set: Use Records or value objects instead.
  • No synchronized blocks: Use java.util.concurrent or Virtual Threads instead.

References