Java Language Patterns

Priority: P0 (CRITICAL)

Modern Java (21+) standards for concise, immutable, and expressive code.

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 are 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.