利用類別特性定義一個圓錐體，並且可以算出體積、表面積

code

package javahomework;

public class HW09 {
 public static void main(String args[]) {
  Cone r1 = new Cone();
  Cone r2 = new Cone(10.0);
  Cone r3 = new Cone(15.0, 20.0);
  System.out.println("Volume is " + r1.volume() + " FaceArea is "
    + r1.facearea());
  System.out.println("Volume is " + r2.volume() + " FaceArea is "
    + r2.facearea());
  System.out.println("Volume is " + r3.volume() + " FaceArea is "
    + r3.facearea());
 }

}

class Cone {
 double r, h;
 double pi = 3.14;

 Cone(double a, double b) {
  r = a;
  h = b;
 }

 Cone() {
  r = 1.0;
  h = 1.0;
 }

 Cone(double a) {
  r = a;
  h = a;
 }

 double volume() {
  return (pi * r * r * h) / 3;
 }

 double facearea() {
  return (Math.pow((r * r) + (h * h), 0.5)) * 2 * pi;
 }
}