Inheritance with the Animal Class

Goals

• Given an inheritance tree and a state chart, use concrete classes, interfaces, and abstract classes to write code for Animals.

Inheritance Tree

State Chart

Note

• That all Animals are born awake. An Animal's initial hunger state is 0 unless specified otherwise in a progeny's constructor.
• A SeeingEyeDog's initial hunger state is .5 because it inherits from Dog.
• +=, -=, /= are short cut operators
  • E.g. hunger += ((1 - hunger)*3/4) is equivalent to hunger = hunger + ((1 - hunger)*3/4).

Tips

• We provide you with code for Animal.java, Canine.java, Dog.java, Trainable.java
• You need to write the following classes based on the Inheritance tree: Feline, Cat, Lion, Wolf, SeeingEyeDog
• Make the instance variables in superclasses protected instead of private . This way, you will be able to access the variables of superclasses. Remember, private means that the variable can only be accessed by the class it is in. protected variables can be accessed outside the class in a more secure fassion than public variables. See example in Animal.java
• In the interest of keeping this project as uncomplicated as possible, the sit() and stand() methods should print "AnimalType sit" and "AnimalType stand" respectively . See example in Dog.java

Constructor and Method Signatures

Constructors:
  Cat()
  Lion()

  Wolf()
  SeeingEyeDog(int trackingCode)
  
Methods:
 	
  In class Cat, Lion, Wolf
    String makeNoise() //concrete method 


  In class Lion
    void sit()  
    void stand()  
	
  In class Cat
     void eat() //override from Animal class
     

  In class Feline
   int getLivesLeft();
   void roam() //concrete method 


   In class SeeingEyeDog
    int getTrackingCode();

Interactions

Some sample interactions are provided to get you started.

---------------Abstract Class and Inheritance-------------

> Animal a = new Animal(); //cannot instantiate abstract class
InstantiationException: 
> Animal a = new Dog();//variable of supertype can hold a subtype
> a.getHunger() //return Dog's hunger state
0.5
> a.makeNoise() //Dog's makeNoise (concrete method) is executed
"bark!"
> a.isAwake()
true
> a.eat(); //eat is inherited by Dog and makes hunger 0
> a.getHunger() 
0.0
> a instanceof Dog //Reference variable a points to dog obeject
true
> a instanceof Canine
true //Dog is subtype of Canine
> a instanceof Animal
true //Animal super super type is Dog
> a instanceof Object
true //Animal is super super type of Dog, and Animal is subtype of Object (implicit or implied)

-----------Interfaces--------------------------
> Lion l = new Lion()
> l.stand()  //stand() is implemented in Lion class
Lion stand
> Trainable beast = new Lion();
> beast.sit(); //calls sit method of the approriate object beast variable is pointing to
Lion sit
> beast.stand();
Lion stand
> beast = new Dog();
> beast.sit();
Dog sit
> beast.stand();
Dog stand
-----------------Inheritance with Concrete Classes-------------
> SeeingEyeDog d = new SeeingEyeDog(5)
> d.getTrackingCode()
5
> d instanceof SeeingEyeDog
true
> d instanceof Dog
true
> d instanceof Canine
true
> d instanceof Animal
true
> d instanceof Object
true

-----------------Some more interactions-------------------------
> Lion l = new Lion();
> l.isAwake()
true
> l.getHunger() //returns hunger state of Lion
0.9
> l.eat();
> l.getHunger()
0.0
> Cat c= new Cat();
> c.getHunger()
0.4
> c.getLivesLeft()
9
> c.makeNoise()
"meow"