class Animal {
    protected String name;
    private int weight;
    public Animal(String n, int w) {
        name = n;
        weight = w;
    }
    public void eat(String food) {
        System.out.println(name + " eats some " + food + ".");
        weight += 0.5;
    }
} // class Animal

class Fish extends Animal {
    private int maxDepth;
    public Fish(String n, int w, int d) {
        super(n, w);
        maxDepth = d;
    }
    public void swim() {
        System.out.println(name + " swims.");
    }
} // class Fish

class Bird extends Animal {
    private int maxAltitude;
    public Bird(String n, int w, int a) {
        super(n, w);
        maxAltitude = a;
    }
    public void fly() {
        System.out.println(name + " flies.");
    }
    public void eat(String food) {
        System.out.println(name + " flutters its wings.");
        super.eat(food);
    }
} // class Bird

class Zoo {
    public static void main(String[] args) {
        Bird tweety = new Bird("Tweety", 3, 1000);
        tweety.eat("corn");
        tweety.fly();

        Fish b = new Fish("Bubbles", 13, 100);
        b.eat("fish food");
        b.swim();

        Animal w = new Fish("Willy", 4000, 1000);
        w.eat("tourists");
        // w.swim(); -- Doesn't work. See below.
    }
} // class Zoo