java-21

Records in Java 21 provide a concise syntax for immutable data carriers. Use the `record` keyword to define a class with final fields, auto-generated constructors, and accessor methods, eliminating boilerplate while enforcing immutability for DTOs and domain objects.

Sealed types restrict which classes can extend or implement a type, creating closed hierarchies. Use sealed types to enforce controlled inheritance, improve pattern matching, and make your codebase's design intent explicit for APIs and domain models.

Virtual threads are lightweight threads managed by the JVM that scale blocking I/O operations efficiently. They allow you to write simple, synchronous code while handling thousands of concurrent connections, dramatically improving throughput for I/O-bound workloads.

Yes. Records provide immutable data structure definitions while sealed types restrict the permitted subtypes. Together, they create type-safe, maintainable hierarchies—ideal for designing clean APIs with strong immutability guarantees and predictable inheritance boundaries.

Use pattern matching with records and sealed types to write exhaustive, readable switch expressions. Apply immutability throughout your module, leverage virtual threads for concurrent I/O, and enforce sealed hierarchies to keep your codebase maintainable and type-safe.