abstract class Animal {
   public abstract void noise();
}

class Dog extends Animal {

   public void noise() {
      System.out.println("Woof!");
   }
}
class Cat extends Animal {

   public void noise() {
      System.out.println("Nyan");
   }
}

public class Test {
   public static void main(String[] args) {
      Dog rover = new Dog();
      Cat roverCat = convert(rover);
      roverCat.noise();
   }

   public static Cat convert(Dog d) {
      Cat[] cats = new Cat[100];
      Animal[] animals = cats;
      animals[0] = d;
      return cats[0];
   }
}