13. Sealed Classes: Controlled Inheritance

Scenario

Java 17 introduced Sealed Classes to allow developers to explicitly state which classes are allowed to extend a class.

Code Block

// Only Circle and Square are allowed to extend Shape
sealed class Shape permits Circle, Square {
    abstract void draw();
}

final class Circle extends Shape {
    void draw() { System.out.println("Drawing Circle"); }
}

non-sealed class Square extends Shape {
    void draw() { System.out.println("Drawing Square"); }
}

// class Triangle extends Shape { } // COMPILE ERROR: Triangle is not permitted

public class Main {
    public static void main(String[] args) {
        Shape s = new Circle();
        s.draw();
    }
}

Take Your Shot

Predicted Output

Type exactly what you think will be printed in the console.