SE-1021 Software Development 2
Lab 4: Barnyard fun with inheritance

Outcomes

• Use inheritance and polymorphism to create classes that exhibit similar interfaces and behaviors

You will write a program that makes use of a number of supplied classes. In addition, you will define an interface and modify some of the supplied classes to implement the interface. Your program will generate a random number of barnyard animal objects. The animal objects will then make sounds and calculate their market value.

Project Setup

• First create the Lab4 project. Download this lab4.zip file; then follow these steps to import it :
  1. With the Lab4 project selected in the Package Explorer select File -> Import...
  2. From the Import dialog select General -> Archive File and click Next
  3. Click the first Browse button to and select the lab4.zip file you downloaded
  4. When you have selected the lab4.zip file click Open and then Finish to complete the import. You will see a folder named src in your project; right-click this folder, and select Build Path/Use this source folder from the context menu. Once part of the build path, you'll see two packages: edu.msoe.se1021.audio and edu.msoe.se1021.YOURLOGIN.
• Rename the edu.msoe.se1021.YOURLOGIN to match your MSOE username (see steps below). Do not modify the edu.msoe.se1021.audio package name.
  1. Select the package name in the package explorer
  2. Right-click and select Refactor -> Rename from the context menu
  3. Enter the new name and click OK

The lab4.zip file includes the following interface and classes:

• Vocalize.java -- An interface for objects that can make sounds (vocalize).
• Livestock.java - An abstract class that implements the behavior and attributes common to all barnyard animals.
• Dog.java -- Represents a dog and implements the Vocalize interface.
• Sheep.java -- Represents a sheep and implements the Vocalize interface.
• Horse.java -- Represents a horse and implements the Vocalize interface.
• Chicken.java -- Represents a chicken and implements the Vocalize interface.
• WavPlayer.java -- Loads and plays a .wav file.

The WavPlayer.java class and Vocalize.java interface (shown in gray in the UML class diagram below) are already complete and do not have to be modified for this assignment.

The 'animal' java files (shown in tan) are mostly complete; you'll have to modify them as described below in Parts 2 and 3.

You'll have to create two files from scratch: Lab4.java and MarketPrice.java (also in tan). These are described in Parts 1-3 below.

Part 1: Make sounds (to be demonstrated before the end of lab)

You must demonstrate proper functionality for Part 1 before the end of lab (worth 15 points).

Create a Lab4 class (in part 1, do not modify any other class or interface files) that contains the following class (i.e., static) methods (consult the UML class diagram and follow it when declaring the methods below) :

Part 2: Implement market price calculation

In addition, you must define a MarketPrice interface for objects that can determine their market price. Be sure to follow the specification illustrated in the UML class diagram, where the abstract Livestock class inherits this interface, which is then "passed through" to the subclasses. You will then need to modify the barnyard animal classes so that they actually implement the MarketPrice interface method. The market price for each type of barnyard animal is determined as follows:

Market Price for Dog

$500 / (age+1)

Market Price for Sheep

The base price is: $1.05 * (weight in pounds).

If the sheep hasn't been shorn recently, the following premium should be added to the price: $0.40 * (height in inches).

Market Price for Horse

If the horse is less than 80% of the maximum age for a horse, then the market price is determined by: $1000 * (the percentage of life remaining for the horse). You should assume that the horse lives to the maximum age of a horse (as specified within the Horse class).

Otherwise, the market price is: $0.12 * (weight in pounds).

Market Price for Chicken

If the chicken is a layer, the market price is: $1 * ( (maximum chicken age) - (age) ).

Otherwise, the market price is: $0.38 * (weight in pounds).

Part 3: Sorting by Market Price - implementing the Comparable<> interface

Once Part 2 is complete, add the following additional functionality to your program (consult the UML class diagram and follow it when declaring the methods below):

• main -- Add the following to the end of the main method written in Part I:
  1. Call sortValuableAnimals to get one List<> containing references to objects (sorted by price, from lowest to highest) that implement the MarketPrice interface.
  2. Pass the returned List<> to displayMarketPrice to cause each animal to display its market price and details about its attributes.
      
• sortValuableAnimals -- Accepts four Lists (one of each type of barnyard animal) and creates one ArrayList<> containing all of the barnyard animals. Once created, this method should call Collections.sort() to re-order the ArrayList<> of animals sorted by market price. To do this, you'll have to modify the Livestock class to implement the Comparable<Livestock> interface so that it implements the compareTo() method of the Comparable<> interface. This method then returns a List<> reference to the sorted array ArrayList<> .
   
• displayMarketPrice -- Accepts a List<> of MarketPrice objects and displays the market price and attributes of each object.
  • You should use the toString method that is already implemented to display the attributes of each object.
  • The output should look something like this, with prices ascending:

          $10.50 for A recently shorn, 2 year old, 28.0 inch tall sheep weighing 10.0 pounds
          $62.50 for A 7 year old, 21.0 inch tall dog weighing 18.0 pounds
          $500.00 for A 6 year old, 52.0 inch tall horse weighing 1315.0 pounds

  • You must format the dollar amounts to always display two places to the right of the decimal. Hint: you may find the DecimalFormat and/or NumberFormat classes useful.

Lab Submission (due date in Blackboard)

1. Demonstrate Part 1 to your instructor.
2. Create a .zip file of the package directory containing all of the classes/interfaces in the edu.msoe.se1021.YOURLOGIN directory (make sure your Lab4.java file is in this directory as well).
3. Upload your files through Blackboard (assignment "Lab 4: Barnyard fun..."). Be sure to keep copies of all your files, in case something gets lost.

Your grade will be based on the following criteria:

• Meeting requirements; your program must compile and run. If you have trouble, you must come to see me. If you don't and you submit a program that does not compile or produce meaningful results will receive a grade of no higher than 50, even after reworking your program.
   
• Technical quality of your program. Technical quality consists of formatting, commenting, and following coding style guidelines.
   
• Spelling and grammar.
   
• Timeliness of submission as stated in the course policies.