package com.shape;

public class Circle extends Shape {
    private double radius;   // 半径

    public Circle(double radius) {
        if (radius <= 0) {
            throw new IllegalArgumentException("半径必须大于0");
        }
        this.radius = radius;
    }

    public double getRadius() {
        return radius;
    }

    public void setRadius(double radius) {
        if (radius > 0) {
            this.radius = radius;
        }
    }

    @Override
    public double getArea() {
        return Math.PI * radius * radius;   // πr²
    }
}