[JAVA] object overloading ex

class Car{
 protected int num;
 protected double gas;

 public Car(){
  num=0;
  gas=0.0;
  System.out.println("生產了車子。");
 }
 public void setCar(int n,double g){
  num=n;
  gas=g;
  System.out.println("將車號設為"+num+"，將汽油量設為"+gas+"。");
 }
 public void show(){
  System.out.println("車號是"+num+"。");
  System.out.println("汽油量是"+gas+"。");
 }
}
class RacingCar extends Car{
 private int course;
 public RacingCar(){
  course=0;
  System.out.println("生產了賽車。");
 }
 public void setCourse(int c){
  course=c;
  System.out.println("將賽車編號設為"+course+"。");
 }
 public void show(){
  System.out.println("賽車的車號是"+num+"。");
  System.out.println("汽油量是"+gas+"。");
  System.out.println("賽車編號是"+course+"。");
 }
}
class Sample4{
 public static void main(String[] args){
  Car cars[]=new Car[2];

  cars[0]=new Car();
  cars[0].setCar(1234,20.5);

  cars[1]=new RacingCar();
  cars[1].setCar(1234,20.5);

  for(int i=0;i<cars.length;i++){
   cars[i].show();
  }
 }
}