Getting Started

Download CS201_Lab08.zip and import it into your Eclipse workspace (File→Import→General→Existing projects into workspace→Archive file.) You should see a project called CS201_Lab08 in the Package Explorer.

Right click on StartLab.java and choose Run As→Java Application. In the console window, type yes when prompted. When the program completes, right click on the project (CS201_Lab08) and choose Refresh. You should see your code from Lab 7.

In this lab, you will add the capability to the classes in the Vehicle class hierarchy to represent the vehicle’s maximum speed, and use this feature to add a capability to the Trip class to determine a vehicle’s average speed on a particular trip.

Your Task

Make the following modifications:

(1) Add a maxSpeed field, with type double, in the Vehicle class. Add a constructor to Vehicle that takes a single double parameter and uses its value to initialize the maxSpeed parameter.

(2) Add a getMaxSpeed accessor method to Vehicle to return the Vehicle’s maximum speed.

(3) Add constructors to Car, Boat, and Airplane taking a single double parameter. Each constructor should call the superclass constructor, passing the parameter value as the argument.

(4) Add the following abstract method to the Vehicle class:

public abstract double getSpeed(Terrain t);

This method returns the speed of the Vehicle over the given kind of terrain. You will need to implement this method in each subclass of Vehicle.

Here are the rules for different kinds of vehicles:

A Car moves at its maximum speed over ROAD terrain, and at one-quarter of its maximum speed over AIRPORT and MARINA terrain.
A Boat moves at its maximum speed over WATER, and at one-quarter of its maximum speed over MARINA.
An Airplane moves at its maximum speed over all kinds of terrain.

If the getSpeed method is called with a terrain type that is not legal for a particular kind of Vehicle, you can throw an IllegalArgumentException:

throw new IllegalArgumentException("Illegal terrain: " + t);

(5) Your JUnit test classes will no longer compile because they assume that Car, Boat, and Airplane objects can be created without passing any arguments to the constructor. Change these tests so that:

The Car object has a maximum speed of 100.
The Boat object has a maximum speed of 50.
The Airplane object has a maximum speed of 500.

Re-run all of the tests to make sure they still pass.

(6) Add the following method to the Trip class:

public double findAverageSpeed(Vehicle v) {
    ...

This method determines the average speed of a given Vehicle traversing the sequence of terrain represented by the Trip object on which the method is called, assuming that the vehicle always moves at its maximum speed. It should compute the total time required for the trip. Let’s say that the trip is composed of terrain types

t₀, t₁, t₂, …, t_n-1

The max speed of a vehicle over terrain value t is

speed(t)

which is what is returned by calling the getSpeed method on the vehicle object and passing the terrain value t.

The total amount of time T required for the trip is

T = (1 / speed(t₀)) + (1 / speed(t₁)) + (1 / speed(t₂)) + … + (1 / speed(t_n-1))

Then, the average speed for the trip is

n / T

(7). Add JUnit tests to CarTest, BoatTest, and AirplaneTest to test the getSpeed and findAverageSpeed methods.

For example:

// in CarTest

private static final double DELTA = 0.00001;

private Trip exampleTrip;
private Car myCar;

protected void setUp() {
  exampleTrip = new Trip(3);
  exampleTrip.setHop(0, Terrain.AIRPORT);
  exampleTrip.setHop(1, Terrain.ROAD);
  exampleTrip.setHop(2, Terrain.MARINA);

  myCar = new Car(100.0); // the Car's maximum speed is 100
}

public void testGetSpeed() {
  // full speed over road
  assertEquals( 100.0, myCar.getSpeed(Terrain.ROAD), DELTA );

  // one-quarter speed through an airport
  assertEquals( 0.25 * 100.0, myCar.getSpeed(Terrain.AIRPORT), DELTA );

  // one-quarter speed through a marina
  assertEquals( 0.25 * 100.0, myCar.getSpeed(Terrain.MARINA), DELTA );
}

public void testFindAverageSpeed() throws Exception {
  double dist = 3.0;
  double time = (1.0/(.25 * 100.0)) + (1.0 / 100.0) + (1.0 / (.25 * 100.0));
  assertEquals( dist /  time, exampleTrip.findAverageSpeed(myCar), DELTA);
}

Submitting

When you are done, submit the lab to the Marmoset server using either of the methods below.

From Eclipse

If you have the Simple Marmoset Uploader Plugin installed, select the project (CS201_Lab08) in the package explorer and then press the blue up arrow button in the toolbar. Enter your Marmoset username and password when prompted.

From a web browser

Save the project (CS201_Lab08) to a zip file by right-clicking it and choosing

Export…→Archive File

Upload the saved zip file to the Marmoset server as lab08. The server URL is

https://cs.ycp.edu/marmoset/