Java

Records and sealed types

Modern Java models data without boilerplate.

record Point(double x, double y) {}

sealed interface Shape permits Circle, Rectangle {}
record Circle(Point center, double radius) implements Shape {}
record Rectangle(Point topLeft, Point bottomRight) implements Shape {}

• Use record for immutable data carriers — equals, hashCode, toString, and accessors for free.
• sealed closes a hierarchy; exhaustive switch replaces instanceof chains.