interface Thing {
	public int age();
}

class Animal implements Thing {

    String name;
    Animal mom;
	
    public int age () {
	return 0;
    }
	
    public void setName (String givenName) {
	name = givenName;
    }
	
    public void setMom (Animal myMom) {
	mom = myMom;
    }
	
    public Animal () {
	System.err.println("An animal is born.");
    }

    public void speak() {
    	System.err.println("I don't know what to do!?");
    }

    public String toString() {
     return "I'm an animal";
     };
} 

class Dog extends Animal {
    public Dog () {
	System.err.println("A dog is born.");
    }
    
    public void speak() {
    	System.err.println("woof");
    }
    
    public void speakLikeAnAnimal() {
	super.speak();
    }
    
    public void fetch() {
    	System.err.println("I'm chasing it as fast as I can!");
    }
}

class Basenji extends Dog {
    public Basenji () {
	System.err.println("A basenji is born.");
    }
	
    public void speak() {
	System.err.println("... (I'm quiet)");
    }
}

class Cat extends Animal {
    public Cat () {
	System.err.println("A cat is born");
    }
    
    public void speak() {
    	System.err.println("meow");
    }
}

public class Animals {
    public static void main(String[] args) { 
    	
	Thing thing1, thing2;
    	Animal animal1, animal2, animal3, animal4;
    	Animal jacksAnimals[] = new Animal[4];
    	Animal jillsAnimals[] = new Animal[4];
    	Dog dog1, dog2;
    	Cat cat1, cat2;
    	Basenji basenji1, basenji2;
    	
    	// basic assignment
    	animal1 = new Animal();
	thing1 = new Animal();
    	dog1 = new Dog();
	thing2 = dog1;
       	dog1.setName("fido");
    	cat1 = new Cat();
    	cat1.setName("fido");
    	System.err.println((dog1.name).equals(cat1.name));
    	System.err.println(dog1.equals(cat1));
    	basenji1 = new Basenji();
    	animal2 = new Dog();
    	dog2 = basenji1;
    	dog2.setMom(dog1);
    	basenji2 = new Basenji();
    	basenji2.setMom(dog1);
    	System.err.println((basenji2.mom).equals(dog2.mom));
        System.err.println(dog2);
    	jacksAnimals[0] = animal1;
    	jacksAnimals[1] = dog1;
    	jacksAnimals[2] = cat1;
    	jacksAnimals[3] = basenji1;
    	for (int i=0; i<4; i++) {
    		jillsAnimals[i] = jacksAnimals[i];
    	}
        System.err.println(jillsAnimals.equals(jacksAnimals));
        
    	
    	System.err.println("Method invocation:");
    	System.err.println("\nWith specific types:");
    	animal1.speak();
    	dog1.speak();
    	cat1.speak();
    	basenji1.speak();

    	System.err.println("\nWith widening:");
    	animal2.speak();
    	dog2.speak();

    	System.err.println("\nWith array of animal type:");
    	for (int i = 0; i < 4; i++) {
    		jacksAnimals[i].speak();
    	}
    	System.err.println();	


    	dog1.fetch();    	
    	// jillsAnimals[1] happens to be a dog, but this yields compilation error
    	// jillsAnimals[1].fetch();

	// okay at compile and run time 
    	((Dog)jacksAnimals[1]).fetch();

	// okay at compile time, but run-time error since jacksAnimals[2] contains a cat
    	//((Dog)jacksAnimals[2]).fetch();
    	
    	
    	// Narrowing Assignments
    
    	//System.err.println("\nNarrowing assignments:");
    	//dog2 = animal1;
    	//dog2 = animal2;
    	
    	// narrowing, with animal2 = a Dog, and a cast
    	cat2 = (Cat) jacksAnimals[2];
    	//dog2.speak();
    	
    	// allowed?
    	//cat2 = (Cat)((Animal)cat1);
    
    }
}