import java.util.ArrayList;

abstract class Animal {

    private String species;

    public Animal() {
    }

    abstract public String makeNoise();

    final public String move(int numSteps) {
        String newString = "";
        while (numSteps > 0) {
            newString += "tramp ";
            numSteps--;
        }
        return newString;
    }

    public static void main(String args[]) {
        Animal cow = new Cow();
        Animal bird = new Bird();
        Duck duck = new Duck();
        Bear bear = new Bear();


        ArrayList<Animal> zoo = new ArrayList<Animal>();
        zoo.add(bird);
        zoo.add(duck);
        zoo.add(cow);
        zoo.add(bear);
        generateCacaphony(zoo);
    }











    static void generateCacaphony(ArrayList<Animal> zoo) {
        for (int i=0; i< zoo.size(); i++) {
            System.out.println(zoo.get(i).makeNoise());
        }
    }
}