编写一个圆类

package com.cn.demo;

public class Circle {
private double radius;
public Circle() {

}
public Circle(double r) {
this.radius=r;
}
public double getArea() {

return 3.14*radius*radius;
}
public double getPerimeter() {
return 2*3.14*radius;
}
public void show() {
System.out.println("圆的半径是："+radius);
System.out.println("圆的面积是："+getArea());
System.out.println("圆的周长是："+getPerimeter());
}
}