// 声明一个密封类
public sealed class Shape
    permits Circle, Rectangle, Square {
    // 定义 Shape 的属性和方法
}
// 圆形类，继承自 Shape
final class Circle extends Shape {
    private double radius;
    // 构造函数和方法
}
// 矩形类，继承自 Shape
final class Rectangle extends Shape {
    private double length;
    private double width;
    // 构造函数和方法
}
// 正方形类，继承自 Shape
final class Square extends Shape {
    private double side;
    // 构造函数和方法
}
public class Main {
    public static void main(String[] args) {
        // 使用密封类
        Shape shape = new Circle();
        // ... 进行操作
    }
}

abstract class Shape {}
final class Circle extends Shape {
    final double radius;
    Circle(double radius) { this.radius = radius; }
}
final class Rectangle extends Shape {
    final double length, width;
    Rectangle(double length, double width) { this.length = length; this.width = width; }
}
final class Square extends Shape {
    final double side;
    Square(double side) { this.side = side; }
}

public class PatternMatchingDemo {
    public static void main(String[] args) {
        Shape shape = new Circle(10);
        String result = switch (shape) {
            case Circle c -> "Circle with radius: " + c.radius;
            case Rectangle r -> "Rectangle with length: " + r.length + " and width: " + r.width;
            case Square s -> "Square with side: " + s.side;
            default -> "Unknown shape";
        };
        System.out.println(result);
    }
}