An interface with a default method in Java
Java interview exercise on Records, classes & interfaces, difficulty 1 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.
Write interface Shape with double area() and a default method describe() returning "<SimpleClassName> with area <area to two decimals>" (String.format("%.2f")). Then records Circle(double radius) and Rect(double width, double height) implementing it.
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.