import java.util.*;

public class CatsAndDogs {
  public static void main(String[] args) {
    ArrayList cats = new ArrayList();
    for(int i = 0; i < 7; i++)
      cats.add(new Cat(i));
    // Not a problem to add a dog to cats:
    cats.add(new Dog(7));
    for(int i = 0; i < cats.size(); i++)
      ((Cat)cats.get(i)).print();
    // Dog is detected only at run-time
  }
} ///:~