COP3330-02 Object Oriented Programming

Spring 2003

Program 4 (Zoo)

Due: March 27, 2003

Objectives:

The objectives of this assignment are to get hands-on experience:

• creating class hierarchies with inheritance
• extending abstract classes
• creating abstract classes
• overriding methods
• overriding abstract methods
• implementing interfaces
• creating interfaces
• downcasting
• managing many classes

Overview:

You will create a hierarchy of animals that belong to a zoo. The superclass of all your animals, ZooAnimal, has been created for you. In addition, a subclass of ZooAnimal called Bird has also been provided. You should use Bird as an example when coding your animal classes. Be careful though; not all animals are exactly like Birds. See below for the specific state and behavior that should belong to each of the animal classes you create.

The ZooAnimal Hierarchy:

Specifics:

Class: ZooAnimal (provided for you)

The root of our hierarchy is the class ZooAnimal. You are to download this class and use it as is. Listed below are the fields and methods of the ZooAnimal class.

Fields:

The name of this ZooAnimal.

protected String name;

A random number generator with a predetermined seed. This should be used in your isHungry methods.

private Random random;

Methods:

Constructor. This method should be reused by your subclasses. (Use Bird’s constructor as an example of reusing the superclass constructor).

public ZooAnimal(String name)

Returns this ZooAnimal’s name.

public getName()

Returns the next random number from random (see above field).

protected double nextRandom()

Returns true if this ZooAnimal is currently hungry. Subclasses must override this.

public abstract boolean isHungry()

Prints to the screen the fact that this ZooAnimal is eating.

public void eat()

Interface: Flyer (provided for you)

All classes that can fly should implement the Flyer interface. You are to download this interface and use it as is. Listed below are the abstract methods of the Flyer class.

Methods:

Print to the screen the fact that the implementing object is flying. This method may or may not adjust the altitude of the implementing object.

void fly()

Returns the current altitude of the implementing object.

int getAltitude()

Class: Bird (provided for you)

Subclasses of the abstract Bird class are animals that can fly. You are to download this class and use it as is. Listed below are the fields and methods of the Bird class.

Fields:

The current altitude of this Bird.

protected int altitude;

Methods:

Constructor. Reuses constructor of superclass.

public Bird(String name)

Overridden abstract method of the superclass ZooAnimal. Birds are hungry 40% of the time. Therefore, isHungry returns true is the random number x that is generated is 0 <= x < 0.40. You should use this as an example for your isHungry methods.

public boolean isHungry

Prints to the screen the fact that this Bird is flying and adjusts this Bird’s altitude.

public void fly

Returns the altitude of this Bird.

public int getAltitude

Class: ZooAnimalTester (provided for you)

You are to download this class and use it as is. This class has only a main method. Use it to test your hierarchy after you’ve completed coding it.

Example (correct) output. If you don’t have this, something is wrong:

Patrick is eating

Below are the classes that you must write.

Class: Eagle

• An Eagle is a Bird.
• It has a constructor that takes a String argument and initializes the name field to the value of the parameter. (Reuse superclass constructor).

Class: Mammal

• A Mammal is a ZooAnimal.
• It has a constructor that takes a String argument and initializes the name field to the value of the parameter. (Reuse superclass constructor).
• The average Mammal is hungry 60% of the time.
• A Mammal is too general to actually instantiate. (Hint: abstract).

Class: Platypus

• A Platypus is a Mammal.
• A Platypus is a Swimmer.
• It has a constructor that takes a String argument and initializes the name field to the value of the parameter. (Reuse superclass constructor).

• A Platypus is hungrier than most Mammals. A Platypus is hungry 75% of the time.

• When a Platypus swims, its depth increases by 5 and it prints to the screen the fact that this Platypus is swimming.

Class: Bat

• A Bat is a Mammal.
• A Bat is a Flyer.
• It has a constructor that takes a String argument and initializes the name field to the value of the parameter. (Reuse superclass constructor).
• When a Bat flies, its altitude increases by 3 and it prints to the screen the fact that this Bat is flying.

Class: Fish

• A Fish is a ZooAnimal.
• A Fish is a Swimmer. (See Bird for a similar example).
• It has a constructor that takes a String argument and initializes the name field to the value of the parameter. (Reuse superclass constructor).

• The average Fish is hungry 20% of the time.

• When a Fish swims, its depth increases by 7 and it prints to the screen the fact that this Fish is swimming

• A Fish is too general to actually instantiate. (Hint: abstract).

Class: Shark

• A Shark is a Fish.
• It has a constructor that takes a String argument and initializes the name field to the value of the parameter. (Reuse superclass constructor).

Interface: Swimmer

• Defines the method void swim(); This method should print to the screen the fact that the implementing object is swimming. This method may or may not adjust the depth of the implementing object. Use Flyer as an example.
• Defines the method int getDepth(); This method should return a positive integer representing the current depth of the animal. Use Flyer as an example.

Class: ZooAnimalTester2

This class has only a main method. In the main method, you are to create an array that holds ZooAnimals. Do not declare your array of type Flyer. In the array, put four Flyers: two Eagles and two Bats, in that order. Give them the names Billy, Susan, Mark, and Julie, in that order. Iterate over the array, downcasting each to Flyer and then calling its fly method. Call its getAltitude method and print this altitude to the screen also.

Example (correct) output. If you don’t have this, something is wrong:

Billy is flying

Altitude: 1

Susan is flying

Altitude: 1

Mark is flying

Altitude: 3

Julie is flying

Altitude: 3

Summary:

• Download 4 classes: ZooAnimal, Bird, Flyer, and ZooAnimalTester.
• Copy these 4 files into your source directory. If you get lost, try following the instructions for Program 2 (bottom of the specs page). The download process is similar.
• Code the rest of the animal classes.
• Tip: Code Swimmer before the classes that use it (i.e. Fish and Platypus).
• Test your code using ZooAnimalTester. Make sure the output matches.
• Code ZooAnimalTester2.
• Run ZooAnimalTester2. Make sure the output matches.
• You can put the classes you write into any package you want. The downloaded classes aren’t in a package so it is recommended that your classes not be in a package (delete the package field when using the JBuilder New Class wizard).

Submittal:

Submittals should follow the program specifications of the class.

Write-up:

There is no write-up required for this program.