import kr.tpc.*; public class TPC21 { public static void main(String[] args) { Dog d=new Dog(); d.eat(); Cat c=new Cat(); c.eat(); c.night(); // Dog.class, Cat.class Animal ani=new Dog(); // upcasting ani.eat(); ani=new Cat(); // upcasting ani.eat(); //ani.night(); //Cat cc=(Cat)ani; //cc.night(); ((Cat)ani).night(); // downcasting } }