Java Idioms and Patterns

Refactoring Java code to use modern Java 17 features involves applying records for simple data carriers, sealed types for restricted hierarchies, and pattern-matching switch for expressive control flow. This skill guides agents to rewrite sources using these idiomatic patterns for cleaner architecture.

Error handling in modern Java applications should model domain errors with specific exception hierarchies, avoid broad catches, and design predictable failure modes. This skill enforces robust error handling patterns to ensure safer and more maintainable Java codebases.

Setting up dependency injection in Java without field injection requires using constructor injection and programming to interfaces. This skill enforces constructor-based DI patterns to keep services testable, decoupled, and aligned with modern maintainable architecture standards.

Testcontainers works with JUnit 5 for Java integration testing by validating behavior with real dependencies. This skill recommends using JUnit 5, AssertJ, parameterized tests, Mockito, and Testcontainers as quality gates to ensure reliable testing strategies.

Optional in Java 17+ codebases should be used appropriately to represent potential absence of values without relying on null. This skill enforces consistent Optional usage patterns alongside modern Java features to write clearer, safer code.

Java Idioms and Patterns applies to modern Java 17+ codebases that need cleaner architecture. It is designed to guide agents generating or refactoring Java sources toward idiomatic practices, making it suitable for upgrading compatible legacy systems.