public class Circle extends Shape{
    private double radius;
    public Circle(double radius){
        if (radius <= 0){
            throw new IllegalArgumentException("半径必须大于0");
        }
        this.radius = radius;
    }
    @Override
    public double getArea() {
        return Math.PI * radius * radius;
    }

    @Override
    public String getShapeName() {
        return "圆形";
    }

    public double getRadius() {
        return radius;
    }
}