Exercise 1:Creating Bank Account Subclasses (Level  2)


In this exercise, you will create two subclasses of the Account class in the Banking project: SavingsAccount  and CheckingAccount. 


Task 1 - Modifying the Account Class

Using a text editor, modify the Account class source file in the src/com/mybank/domain directory. This class must satisfy the UML diagram in Figure 6-1 on page Lab 6-2; in particular, the balance attribute and Account class constructor are now  protected (indicated by the # character instead of the   -  character ).
  1. Change the  balance attribute from private to protected.
  2. Change the Account constructor from private to protected.

Task 2 - Creating the SavingsAccount Class

Using a text editor, create the SavingsAccount class source file in the  src/com/mybank/domain/ directory. This class must satisfy the UML diagram in Figure 6-1 on page Lab 6- 2 and the business rules defined in the introduction to "Exercise 1: Creating Bank Account Subclasses (Level 1)" on page  Lab 6-2.

Task 3 - Creating the CheckingAccount Class

Using a text editor, create the CheckingAccount class source file in the  src/com/mybank/domain/ directory. This class must satisfy the UML diagram in Figure 6-1 on page Lab 6- 2 and the business rules defined in the introduction to "Exercise 1: Creating Bank Account Subclasses (Level 1)" on page  Lab 6-2.
  1. Declare  the CheckingAccount  class in the  com.mybank.domain package. The CheckingAccount class inherits from the Account class.
  2. Add the overdraftAmount atribute to the CheckingAccount class.
  3. Add a public constructor that takes two arguments: initBalance and overdraftAmount. Pass the initBalance parameter to the super constructor. Save the overdraftAmount parameter to the instance variable.
  4. Add a second  public constructor that takes only one argument: initBalance. Call the first constructor with the initBalance parameter and use the default value 0.0 for the overdraftAmount parameter.
  5. Override the withdraw method to use the overdraftAmount variable. Here is the pseudo-code for the withdraw method:
    if balance < amount
      then
        overdraftNeeded = amount -balance
        if overdraftAmount < overdraftNeeded
          then   transaction fails
          else
            balance = 0
            decrement overdraftAmount by overdraftNeeded
      else
        decrement balance by amount
       

Task 4 - Copying the TestBanking Class

Copy the TestBanking.java file file from the resources/mod06_class1/ directory into the src/com/mybank/test directory.

Task 5 - Compiling the  TestBanking Program

On the command line, use the javac command to compile the test program.

Task 6 - Running the  TestBanking Program

On the command line, use the java command to run the test program. You should see the output listed on page Lab 6-4.: