java中通过父类引用创建子类对象后，输出子类的属性值不是子类中所写的属性值，而是继承父类的，为什么
package com.hu;
public class Vehicle {
public int num;
public String mode;
public String type;
public void ability(){
System.out.println("交通工具具有载人出行的能力");
System.out.println("num:"+num+"\nmode:"+mode+"\ntype:"+type);
}
}
public class Car extends Vehicle {
public int num=6;
public String mode="陆行";
public String type="汽车";
public void ability(){
System.out.println("汽车具有载人陆行的能力");
System.out.println("num:"+num+"\nmode"+mode+"\ntype"+type);
}
@Override
public String toString() {
return "Car [num=" + num + ", mode=" + mode + ", type=" + type + "]";
}
public class Initail { public static void main(String[] args) {
Vehicle vehicle = new Vehicle();
Vehicle car = new Car();
vehicle.ability();
System.out.println();
car.ability();
System.out.println();
System.out.println(car.num+"\n"+car.mode+"\n"+car.type);//就是这行
System.out.println();
System.out.println(car);
}
}为什么
System.out.println(car.num+"\n"+car.mode+"\n"+car.type);
这句输出的是
0
null
null
而不是
6
陆行
汽车
