Individual skill
java
Use when writing, reviewing or refactoring modern Java (21+, 25 LTS) — records and sealed interfaces as algebraic data types, exhaustive pattern-matching switch over instanceof ladders, virtual-thread concurrency, structured concurrency and ScopedValue replacing ThreadLocal, Stream and Optional pipelines, compact-constructor validation, parametrized JDBC, and the Maven/Gradle build surface. NOT Spring framework wiring (that is `spring-boot`).
skills/java/SKILL.md
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- License
- MIT
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SKILL.mdcore · 18,321 bytesSKILL.mdcore · 18,321 bytesSKILL.mdcore · 18,321 bytesevals/README.mddoc · 1,783 bytesevals/cases.yamlasset · 4,630 bytesreferences/builds.mddoc · 5,153 bytesreferences/concurrency.mddoc · 5,106 bytesreferences/streams.mddoc · 4,081 bytesscripts/verify.shruns · 3,302 bytes
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# Modern Java (21+)
Write, review, and refactor Java the way the language is shaped today, not the way it
was in 2014.
Targets **Java 21+ with Java 25 as the current LTS** (released 2025-09-16, supported to
2033; Java 26 is the current non-LTS, 2026-03-17). "Modern" here means: records and sealed
interfaces instead of JavaBeans and type hierarchies, exhaustive pattern-matching `switch`
instead of `instanceof`+cast ladders, virtual threads instead of hand-tuned pools, and
`ScopedValue` instead of `ThreadLocal`. If you are reaching for a telescoping constructor,
a getter/setter bean, or a manual `ExecutorService` sized to a core count, stop.
## When to use / When NOT to use
