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CS 1054 Introduction to Programming in Java (Spring 2008)

Lab 2: Using Objects

Lab Objectives

• To learn how to create and manipulate objects using BlueJ.
• To learn how to write programs that test and use objects.

Instructions

1. Download ObjectExamples.zip , save the file, and then extract it in a folder you can locate. This is a BlueJ project that contains code for three classes: LightBulb, Car, and BankAccount.
2. Make sure these classes are compiled properly: right-click on each icon and choose "Compile".
3. Create one object of each class (right-click on the icon, and select "new ..."). Execute methods on the objects as your instructor did in class (right-click on the red icons, and select the appropriate methods).
4. For the BankAccount class, interactively within BlueJ, carry out the following:
   • Create a BankAccount object called bob.
   • Create a BankAccount object called mary.
   • Deposit 1000 dollars to bob's account.
   • Deposit 2000 dollars to mary's account.
   • Withdraw 150 dollars from mary's account.
   • Deposit 200 dollars to bob's account.
   • check the balance of bob's account (it should be 1200.0)
   • check the balance of mary's account (it should be 1850.0)
5. Within the same project, create a Java class (select "New Class") called BankAccountTester (BankAccountTester.java). Use the following code (cut and paste, if you like, but make sure you place the correct name and date):

   ---

   // -------------------------------------------------------------------------
   /**
    *  This class tests the BankAccount class;
    *  it creates two bank account objects and calls deposit, withdraw
    *  and getBalance methods on the objects
    *  
    *  @author  your-pid
    *  @version (place the date here)
    */
   
   public class BankAccountTester
   {
       public static void main( String args[] )
       {
           BankAccount bob = new BankAccount();
           BankAccount mary = new BankAccount();
           
           bob.deposit( 1000.00 );
           mary.deposit( 2000.00 );
           mary.withdraw( 150.00 );
           bob.deposit( 200.00 );
           
           double bobsBalance = bob.getBalance();
           double marysBalance = mary.getBalance();
           
           System.out.print( "Bob's balance is " );
           System.out.println( bobsBalance );
           System.out.print( "Mary's balance is " );
           System.out.println( marysBalance );
       }
   
   }
   
   

   ---

   You will notice that the code is a program that does exactly the same thing you did in the previous item, except that you are doing it through a separate Java program, instead of interactively through BlueJ.
6. You will now do something similar for the Car class. First, interactively through BlueJ:
   • Create a single Car object called myRaceCar
   • Drive 300 miles
   • Load 2 gallons of gas
   • Drive 30 miles
   • Check the amount of gas left (should be 3.8 gallons left)
   • Check the distance travelled (should be 330 miles total)
7. Now, here's the hardest part: Write a CarTester program (use BankAccountTester as a pattern) that carries out exactly the same actions as the previous item.
8. Check with your TA regarding grading instructions. He will need to make sure that you have carried out all these steps.