This is the finished BankAccount class. I am also including the Transactions class although we did not fill in the transactions class with anything of interest. As practice for the exam, you might finish the Transactions class -- i.e., inside the main method of the Transactions class use the dot operator to call methods on the account.
This is the SimpleBankAccount, SimpleBank, and SimpleTransactions classes. The SimpleBankAccount class is a simplified version of the BankAccount class above. The SimpleBank class illustrates that you can both pass objects as parameters (see the transfer method) as well as return objects as return value (see the openAccount method).
As per Chloe's request, I am also including the two classes I wrote on the fly in class today!