core-java-jvm-engineering

name	core-java-jvm-engineering
description	Use this skill when implementing or reviewing core Java logic, domain models, performance-sensitive code, or JVM-related concerns in a Spring Boot microservice.

When applying Core Java & JVM Engineering skills, follow these rules strictly:

1. Use Java 17 (LTS) language features:

   • Records for immutable DTOs
   • Sealed classes where domain constraints apply
   • Optional only for return types, never fields
   • Streams only when they improve clarity

2. Enforce immutability by default:

   • Domain entities must expose behavior, not setters
   • Use constructors for mandatory invariants

3. Handle exceptions deliberately:

   • Never catch Exception or RuntimeException generically
   • Use domain-specific exceptions
   • Avoid exception-driven control flow

4. Be JVM-aware:

   • Avoid unnecessary object creation in hot paths
   • Prefer composition over inheritance
   • Avoid reflection unless required by Spring

5. Write code that is:

   • Readable without comments
   • Deterministic
   • Testable in isolation

Never introduce cleverness at the cost of clarity.