Pattern Matching for Switch

public class PatternMatchingSwitch {

    sealed interface Shape permits Circle, Rectangle, Triangle {}
    record Circle(double radius) implements Shape {}
    record Rectangle(double width, double height) implements Shape {}
    record Triangle(double base, double height) implements Shape {}

    static double area(Shape shape) {
        return switch (shape) {
            case Circle c -> Math.PI * c.radius() * c.radius();
            case Rectangle r -> r.width() * r.height();
            case Triangle t -> 0.5 * t.base() * t.height();
        };
    }

    static String describe(Object obj) {
        return switch (obj) {
            case null -> "null";
            case Integer i when i > 0 -> "positive integer: " + i;
            case Integer i -> "non-positive integer: " + i;
            case String s when s.length() > 10 -> "long string";
            case String s -> "short string: " + s;
            case int[] arr -> "int array of length " + arr.length;
            default -> "unknown type: " + obj.getClass().getSimpleName();
        };
    }

    public static void main(String[] args) {
        Shape circle = new Circle(5);
        Shape rect = new Rectangle(4, 6);
        Shape tri = new Triangle(3, 8);

        System.out.println("Circle area: " + area(circle));
        System.out.println("Rectangle area: " + area(rect));
        System.out.println("Triangle area: " + area(tri));

        System.out.println(describe(42));
        System.out.println(describe(-5));
        System.out.println(describe("hello"));
        System.out.println(describe("a very long string here"));
        System.out.println(describe(new int[]{1, 2, 3}));
        System.out.println(describe(null));
    }
}