java中的多态

引用的多态

/javaDemo4/src/com/imooc/Animal.java

package com.imooc;public class Animal {    }

/javaDemo4/src/com/imooc/Dog.java

package com.imooc;public class Dog extends Animal {}

/javaDemo4/src/com/imooc/Initail.java

package com.imooc;public class Initail {    public static void main(String[] args) {        Animal obj1 = new Animal();        Animal obj2 = new Dog();  //父类的引用是可以指向子类对象        //Dog obj3 = new Animal();  //报错    }}

方法多态

/javaDemo4/src/com/imooc/Animal.java

package com.imooc;public class Animal {    public void eat() {        System.out.print("动物具有吃的能力");    }}

/javaDemo4/src/com/imooc/Dog.java

package com.imooc;public class Dog extends Animal {    public void eat() {        System.out.print("狗具有吃肉的能力");    }    public void watchDoor() {        System.out.print("狗具有看门的能力");    }}

/javaDemo4/src/com/imooc/Initail.java

package com.imooc;public class Initail {    public static void main(String[] args) {        // TODO Auto-generated method stub        Animal obj1 = new Animal();        Animal obj2 = new Dog();  //父类的引用是可以指向子类对象        //Dog obj3 = new Animal();  //报错        Animal obj3 = new Cat();        obj1.eat();                obj2.eat();        obj3.eat();//        obj2.watchDoor();    }}