public class Circle extends Shape {
    private double radius;
    
    // 构造方法
    public Circle(double radius) {
        this.radius = radius;
    }
    
    // 实现抽象方法，计算圆的面积
    @Override
    public double getArea() {
        return Math.PI * radius * radius;
    }
    
    // getter和setter方法
    public double getRadius() {
        return radius;
    }
    
    public void setRadius(double radius) {
        this.radius = radius;
    }
}