java-fundamentals

Java 21 records provide a concise syntax for creating immutable data carriers, automatically generating constructors, accessors, and equality methods. You can use them to build robust DTOs and value objects with minimal boilerplate across your Java projects.

Sealed classes restrict which types can extend a hierarchy, enabling exhaustive pattern matching in switch statements. You should use sealed types when modeling closed domain logic, allowing the compiler to verify that all possible cases are handled safely and concisely.

Virtual threads are the best way to handle high-throughput I/O-bound concurrency in Java 21. They allow you to create millions of lightweight threads with minimal overhead, simplifying concurrent programming without requiring complex reactive frameworks.

Yes, you can refactor existing class hierarchies into sealed types to gain compile-time exhaustiveness checks. By sealing your interfaces and classes, you ensure that pattern matching switch expressions cover all permitted subtypes without needing a default case.

Java 21 pattern matching fully supports guarded switch logic using conditional expressions within case labels. This allows you to combine type patterns with boolean conditions to express complex domain rules concisely and safely within a single switch statement.