多态性的应用

package com.yikuan.cn;

class A1{
public void tell1(){
System.out.println("A--tell1");
}
}

class B1 extends A1{
public void tell2(){
System.out.println("B--tell2");
}
}

class C1 extends A1{
public void tell3(){
System.out.println("C--tell3");
}
}

public class Test1 {
public static void main(String[] args) {
say(new B1());
say(new C1());
}
public static void say(A1 a){
a.tell1();
}

/*public static void say(B1 b){
b.tell1();
}
public static void say(C1 c){
c.tell1();
}*/
}