Java™ How to Program, Seventh Edition

M.9. Class Transaction

Class Transaction (Fig. M.8) is an abstract superclass that represents the notion of an ATM transaction. It contains the common features of subclasses BalanceInquiry, Withdrawal and Deposit. This class expands upon the “skeleton” code first developed in Section 10.9. Line 4 declares this class to be abstract. Lines 6–8 declare the class’s private attributes. Recall from the class diagram of Fig. 10.22 that class Transaction contains an attribute accountNumber (line 6) that indicates the account involved in the Transaction. We derive attributes screen (line 7) and bankDatabase (line 8) from class Transaction’s associations modeled in Fig. 10.21—all transactions require access to the ATM’s screen and the bank’s database. ...