التصريح بالأنواع المختومة

public class Main {
    sealed interface Shape permits Circle, Square {}
    record Circle(double radius) implements Shape {}
    record Square(double side) implements Shape {}

    public static void main(String[] args) {
        Shape s = new Circle(2.0);
        System.out.println(s);
    }
}

public class Main {
    sealed interface Animal permits Dog, Cat {}
    static final class Dog implements Animal {
        public String toString() { return "Dog"; }
    }
    static final class Cat implements Animal {
        public String toString() { return "Cat"; }
    }

    public static void main(String[] args) {
        Animal a = new Dog();
        System.out.println(a);
    }
}

public class Main {
    sealed interface Plugin permits CorePlugin, ExternalPlugin {}
    static final class CorePlugin implements Plugin {}
    static non-sealed class ExternalPlugin implements Plugin {}
    static class ThirdParty extends ExternalPlugin {}

    public static void main(String[] args) {
        Plugin p = new ThirdParty();
        System.out.println(p.getClass().getSimpleName());
    }
}

public class Main {
    sealed static abstract class Expr permits Num, Add {}
    static final class Num extends Expr {
        final int value;
        Num(int value) { this.value = value; }
    }
    static final class Add extends Expr {
        final Expr left, right;
        Add(Expr left, Expr right) { this.left = left; this.right = right; }
    }

    public static void main(String[] args) {
        Expr e = new Add(new Num(1), new Num(2));
        System.out.println(e.getClass().getSimpleName());
    }
}

public class Main {
    sealed interface Json permits JsonNull, JsonNumber, JsonString {}
    record JsonNull() implements Json {}
    record JsonNumber(double value) implements Json {}
    record JsonString(String value) implements Json {}

    public static void main(String[] args) {
        Json[] values = { new JsonNull(), new JsonNumber(3.5), new JsonString("hi") };
        for (Json j : values) {
            System.out.println(j);
        }
    }
}