Override Labs

In this lab we will use polymorphism to customize class behavior, and create methods to use this functionality.

Polymorphism/com.example.polymorphism.labs.vehicles

  1. Vehicle has a toString() method. Use Eclipse to add a toString() method to the subclasses Boat, Automobile, and Truck.
  2. With a class open, choose Source (right-click or ⌘⌥S).

  3. Choose Generate toString()...

    Source->Generate toString() * Choose the fields to include in the toString() method, and any information from superclasses (via getters).

    Choose fields and methods

  4. Add the method public double calculateRegistrationFee(double rate) to Vehicle.

  5. Return 0.0. This method is a stub.
  6. Use Eclipse to override calculateRegistrationFee in Boat.
  7. With a class open, choose Source (right-click or ⌘⌥S).

  8. Choose Override/Implement Methods...

    Source->Override/Implement Methods * Choose the methods to override from superclasses.

    Choose fields and methods * Functionality: if a boat is 30 feet in length or more, double the rate and multiply by the purchasePrice. Otherwise multiply by the rate by the purchasePrice. 4. Override calculateRegistrationFee in Automobile. * Functionality: multiply the rate by the purchasePrice. 5. Override calculateRegistrationFee in Truck. * Functionality: if the numberOfWheels is 6 or more, multiply rate by 1.5 and multiply by the purchasePrice. Otherwise multiply the rate by the purchasePrice.

We will use JUnit tests to verify our calculateRegistrationFee methods work. Note that these classes belong in the test source directory. 1. test/com.example.polymorphism.labs.vehicles.VehicleTests * Uncomment the assertEquals(double, double, double) method call. * Run As->JUnit Test to verify that Vehicle functions as expected. 2. test/com.example.polymorphism.labs.vehicles.AutomobileTests * Uncomment the test method and run the class. Fix any bugs in your Automobile code. 3. test/com.example.polymorphism.labs.vehicles.BoatTests * Uncomment the existing test method and run the class. * Add an appropriately named method to test if rate times two times the purchasePrice is returned for lengths greater than or equal to 30. 4. Create new JUnit Test Case TruckTests. * Add a method to test calculateRegistrationFee returns rate times purchasePrice for under six wheels. * Add a method to test calculateRegistrationFee returns rate times purchasePrice times 1.5 for six or more wheels.

The last task is to create a method to calculate the registration fee for any vehicle. 1. com.example.polymorphism.labs.vehicles.VehicleApp * Add a method calculateVehicleRegistration that has a Vehicle parameter and returns a double. * Functionality: calculate the Vehicle's registration fee with the rate 0.05. * Calculate the registration fee for each Vehicle, and print the purchase price and registration fee.

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