public class Circle {
private double r;//圆的半径
public Circle(double r){
this.r = r;
}
//求圆的面积
public double getArea(){
return Math.PI*r*r;
}
//求圆的周长
public double getPerimeter(){
return 2*Math.PI*r;
}
public static void main(String args[]){
System.out.println("圆的半径 :10");
Circle c1 = new Circle(10.0);
System.out.println("圆的面积 :" + c1.getArea());
System.out.println("圆的周长 :" + c1.getPerimeter());
System.out.println("\n圆的半径 :20");
Circle c2 = new Circle(20.0);
System.out.println("圆的面积 :" + c2.getArea());
System.out.println("圆的周长 :" + c2.getPerimeter());
}
}
运行结果:
圆的半径 :10
圆的面积 :314.1592653589793
圆的周长 :62.83185307179586
圆的半径 :20
圆的面积 :1256.6370614359173
圆的周长 :125.66370614359172