父类指向子类对象

class Fu {
    int num = 5;
}

class Zi extends Fu {
    //int num = 4;
    void show(){
        System.out.println(this.num);//注意看这,子类的方法
    }
}

public class zihefu {

    public static void main(String[] args) {
        Zi z = new Zi();
        z.show();
        System.out.println(z.num + "....." + z.num);

    }
}