Java polymorphic parent class calls method of subclass

package test1;

Java polymorphic parent class calls the method of the subclass

//多态的体现
import javax.print.attribute.standard.RequestingUserName;
import java.util.Scanner;
public class testfather {
public static void main(String[] args)
{
Animal a  = new fish();   //父类对象被赋以子类类型
/*Animal a;
fish b = new fish b;
a= b
;      //向上转型，不丢失精度
a.talk();*/       //可达到相同效果
a.talk();      //fish覆写animal talk方法
Animal c = new bird();
//C.talk2();    //不能实现，因为animal中没有此方法，必须向下转型
   bird b = (bird)c;    //如果不进行转换，父类无法看到子类新扩充的方法
   b.talk2();
}
}
class Animal
{
public void talk()    //如果父类方法不想被覆写，可改为public 
static
 void talk()
{
System.out.println("walk");
}
}
class fish extends Animal
{
public void talk()
{
System.out.println("swim");
}
}
class bird extends Animal
{
public void talk()
{
System.out.println("fly");
}
public void talk2()//父类中没有此方法，调用必须进行强制转换,向下转型。
{
System.out.println("i am a bird");
}
}

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