Introduction to Classes, Objects, Methods and Strings - Java: How to Program Early Objects - page 89

Line 33 prompts the user to enter a deposit amount for account2 . Line 34 obtains the
input from the user by calling Scanner object input 's nextDouble method. Lines 35-36
display the depositAmount . Line 37 calls object account2 's deposit method with
depositAmount as the method's argument ; then method deposit adds that value to the
balance . Finally, lines 40-43 output the name s and balance s of both Account s again to
show that only account2 's balance has changed.
Duplicated Code in Method main
The six statements at lines 13-14, 15-16, 28-29, 30-31, 40-41 and 42-43 are almost
identical —they each output an Account 's name and balance . They differ only in the name
of the Account object— account1 or account2 . Duplicate code like this can create code
maintenance problems when that code needs to be updated—if six copies of the same code
all have the same error or update to be made, you must make that change six times, without
making errors . Exercise 3.15 asks you to modify Fig. 3.9 to include a displayAccount
method that takes as a parameter an Account object and outputs the object's name and
balance . You'll then replace main 's duplicated statements with six calls to displayAc-
count , thus reducing the size of your program and improving its maintainability by having
one copy of the code that displays an Account 's name and balance .
Software Engineering Observation 3.4
Replacing duplicated code with calls to a method that contains one copy of that code can
reduce the size of your program and improve its maintainability.
UML Class Diagram for Class Account
The UML class diagram in Fig. 3.10 concisely models class Account of Fig. 3.8. The dia-
gram models in its second compartment the private attributes name of type String and
balance of type double .
Account
- name : String
- balance : double
«constructor» Account(name : String, balance: double)
+ deposit(depositAmount : double)
+ getBalance() : double
+ setName(name : String)
+ getName() : String
Fig. 3.10 | UML class diagram for Account class of Fig. 3.8.
Class Account 's constructor is modeled in the third compartment with parameters name
of type String and initialBalance of type double . The class's four public methods also
are modeled in the third compartment—operation deposit with a depositAmount param-
eter of type double , operation getBalance with a return type of double , operation set-
Name with a name parameter of type String and operation getName with a return type of
String .