한빛미디어

class inheritanceExample8
{
    public static void main(String args[])
    {
        EmailSender obj1=new EmailSender("생일축하합니다", "고객센터","xx@xx.com", "10%쿠폰");
        SMSSender obj2=new SMSSender("생일축하합니다","고객센터","00-000-000","10%쿠폰);


        send(obj1,"yy@yy.com");
        send(obj1,"zz@zz.com");
        send(obj2, "00-000-0000");
    }

    static void send(MessageSender obj, String recipient)
    {
        obj.sendMessage(recipient);
    }
}


예제가 이건데 send(obj1 .......)여기부터 이해가안되서요 ㅠㅠ
갑자기 send가 왜 나온건가요?ㅠㅠ