如何在main方法里调用子类中独有方法？

Question

package com.imooc;

public class Dog extends Animal {
   public void eat(){
    System.out.println("狗是吃肉的");
   }
   public void watchDoor(){
    System.out.println("狗具有看门的能力");
   }
}

package com.imooc;

public class Initail {

 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub
        Animal obj1 = new Animal();
        Animal obj2 = new Dog();//父类指向子类
        Animal obj3 = new Cat();
        obj1.eat();
        obj2.eat();
        obj3.eat();
        ——————？
 }

}

Answer 1

强转为子类类型,然后调用子类独有方法 Animal obj2 = new Dog(); (Dog)obj2.watchDoor();