Identify and apply functional exception handling best practices in Java to improve error clarity, maintainability, and performance by eliminating exception overuse in favour of monadic error types.
Prerequisites: Run ./mvnw validate or mvn validate before applying any changes. If validation fails, stop immediately — do not proceed until the project is in a valid state. Also confirm the VAVR dependency (io.vavr:vavr) and SLF4J are present when introducing Either types.
Core areas: Optional for nullable values over throwing NullPointerException or NotFoundException, VAVR Either for predictable business-logic failures, CompletableFuture for async error handling, sealed classes and records for rich error type hierarchies with exhaustive pattern matching, enum-based error types for simple failure cases, functional composition with flatMap/map/peek/peekLeft for chaining operations th...
Use when you need to apply functional exception handling best practices in Java — including replacing exception overuse with Optional and VAVR Either types, designing error type hierarchies using sealed classes and enums, implementing monadic error composition pipelines, establishing functional control flow patterns, and reserving exceptions only for truly exceptional system-level failures. Part of the skills-for-java project Source: jabrena/cursor-rules-java.