Java 多态

package my_test;

public class Main {
    public static void main(String[] args) {
        Dog d1;//d1是一个引用
        d1=new Dog();//d1 指向父类Dog创建的对象
        d1.say();
        d1.move();
        System.out.println(d1.name);
        System.out.println("------------------------------------------");
        d1=new SDog();//d1 指向子类SDog创建的对象，上面失去引用的对象会被回收
        d1.say();
        d1.move();
        System.out.println(d1.name);
        System.out.println("------------------------------------------");
        //d1.sd();//报错，因为Dog中没有sd()方法.The method sd() is undefined for the type Dog
        d1=new BDog();
        d1.say();
        d1.move();
        System.out.println(d1.name);
        //d1.bd();//报错，同上
        System.out.println("------------------------------------------");
        d1=new SDog_son();//d1 指向孙类SDog_son创建的对象，上面失去引用的SDog对象会被回收
        d1.say();
        d1.move();
        System.out.println(d1.name);
        System.out.println("------------------------------------------");
    }

}
class Dog {
    String name="dog";
    public void say() {
        System.out.println("dog_say");
    }
    public static void move() {
        System.out.println("dog_move");
    }
    
}

class SDog extends Dog{
    String name="sdog";
    public void say() {
        System.out.println("sdog_say");
    }
    public static void move() {
        System.out.println("sdog_move");
    }
    public void sd() {
        System.out.println("sdog自己独特的方法sd");
    }
    
}

class BDog extends Dog{
    String name="bdog";
    public void say() {
        System.out.println("bdog_say");
    }
    public static void move() {
        System.out.println("bdog_move");
    }
    public void bd() {
        System.out.println("bdog自己独特的方法bd");
    }
}

class SDog_son extends SDog{
    String name="sdog_son";
    public void say() {
        System.out.println("sdog_son_say");
    }
    public static void move() {
        System.out.println("sdog_son_move");
    }
}


class Factory{//没有报错，将用于工厂方法模式
    public Dog createdog(int id) {
        if(id==1)
            return new Dog();
        else if(id==2)
            return new SDog();
        else 
            return new BDog();
    }
}