Lab22: Car objects


The goal for this activity is to implement a Car class so that it conforms to the UML below:

Part 1: Driver, Constructor and toString

  1. Create two Java class files: and Only should include a main method.
  2. Add the three instance variables from the UML diagram to your Car class.
  3. Code the constructor for your Car class. This should intialize the make and year fields using the arguments to the constructor. The speed should be initialized to 0.
  4. Code the toString method. This method should take no parameters and should return a string generated using the String.format method:

    String.format("A %d %s that is going %.1f mph", year, make, speed)
  5. Test your partially completed Car class by adding code to the main in that creates and prints two car objects. The contents of main should look something like the following.
    Car car1;
    Car car2;
    car1 = new Car("Ford", 1997);
    car2 = new Car("Toyota", 2014);

Part 2: Remaining Methods

Complete each of the remaining methods of the Car class. Test each method by adding appropriate calls to main.

  • The three "getter" methods should each return the value of the appropriate instance variable.
  • The accelerate method should increase the current speed of the car by 5.0 mph. It should NOT be possible to increase the speed beyond 150.0 mph. If a call to accelerate would push the speed beyond 150.0, the speed should be set to 150.0.

    (How will you test that this is working correctly? How many times do you need to call accelerate before the upper speed limit is reached? Might a loop be helpful here?)
  • The brake method should decrease the current speed by 5.0 mph. It should not be possible for the speed to drop below 0 mph.

Submit through AutoLab by the end of the day. AutoLab will not run Checkstyle tests on your submission. Here are the AutoLab tests in case you want to test locally before submitting

Part 3: Viewing Variables - JGrasp Viewer Canvas (optional)

Use the "viewer canvas" feature of JGrasp to run your main method interactively: Instead of clicking on the run button, click on run canvas. This should allow you to step through your main one instruction at a time. You should be able to inspect the contents of your variables by dragging them from the "Variables" tab into the viewer canvas window.

To see your variables in Eclipse, you would need to run the Debugger. If you are interested, check out Norm Krumpe's Debugger Tutorial (~15 min) which covers basic vocabulary and explains how to track variables in different areas in the Eclipse screen.


Thank you to Dr. Sprague for this activity.


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