Record patterns in Java
Java interview exercise on Modern Java, difficulty 2 of 3. Solve it in the editor beside a worked example, or cold in Interview mode with the example hidden; the tests run the moment you do.
Given sealed interface Shape permits Circle, Square, Rect with records Circle(double radius), Square(double side) and Rect(double width, double height), write area(shape) as a switch with record patterns that deconstruct each shape into its components (case Circle(double r) -> ...). No default: the sealed interface makes it exhaustive.
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Interview mode hides the example: solve it from memory, without the hint or the solution, and it counts as solved cold. Progress is saved in your browser, and in your account if you sign in.