Transcript Objects First With Java

Lab 10: Bank Account II
Transaction List, error checking &
aggregation
Last time we created a BankAccount class:
1. Fields to store:
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Current balance
Account number
Customer name
Customer address
* Think about what types these should be. For example,
should the account number actually be stored as a number?
What about leading 0’s?
2. Write a constructor that takes the customer’s name,
address, and account number, and initializes the
balance to 0.
3. Write getter and setter methods for the name and
address fields.
4. Write a deposit and a debit method.The method
signatures are similar in that there is no return value
and one parameter.
Created by Emily Hill & Jerry Alan Fails
And we tested BankAccount in main:
4. Write a print method that prints out the account information,
including the current balance. Make sure to use proper
formatting so both dollars and cents are displayed
correctly. This method should take no parameters and
return nothing.
5. Write a main method that creates a new, empty
BankAccount stored in local variable myBankAccount.
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Deposit $5.00 into your BankAccount & print the balance
Debit $1.50 into your BankAccount & print the balance
6. Before submitting make sure your BankAccount has the
following methods:
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1 constructor only (not 2) that takes 3 parameters
getCustomerName, getCustomerAddress, getAccountNumber
setCustomerName, setCustomerAddress
Created by Emily Hill & Jerry Alan Fails
deposit, debit, print, main
Today we will
• Update debit to check the balance before deducting
• Update debit & deposit to only work with positive
values
• Add a Transaction class too keep track of all
deposits and debits
• Create new deposit and debit methods that also
take a String description as a parameter
• Create a printSummary method that prints all the
transactions
Created by Emily Hill & Jerry Alan Fails
The if Statement
if is a Java
reserved word
The condition must be a
boolean expression. It must
evaluate to either true or false.
if ( condition )
statement;
If the condition is true, the statement is executed.
If it is false, the statement is skipped.
Copyright © 2012 Pearson Education, Inc.
The if-else Statement
if ( condition )
statement1;
else
statement2;
• If the condition is true, statement1 is executed; if
the condition is false, statement2 is executed
• One or the other will be executed, but not both
Copyright © 2012 Pearson Education, Inc.
Extending BankAccount with if
7. Modify the debit method to make sure there are
sufficient funds before deducting from the
balance. Print an error message if there are
insufficient funds. Test this in main.
8. Modify the debit & deposit methods so that
negative amounts have no effect. For example,
myBankAccount.deposit(5) will add $5, but
myBankAccount.deposit(-5) will do nothing.
Test this in main.
Created by Emily Hill & Jerry Alan Fails
Aggregating
Objects:
Transaction
Should already be
implemented
New additions
Adding a Transaction class
9. Create a Transaction class & enumerated type:
* You can use Eclipse’s source code generation to
create getters and setters for the fields
10.Create an ArrayList field in BankAccount to store a
list of Transactions, & initialize it in the constructor.
But we’ll need one more concept…
Aggregating
Objects:
Transaction
Grouping (i.e., collecting) objects
• Many applications involve collections of objects:
– Personal organizers.
– Library catalogs.
– Student-record system.
• The number of items to be stored varies.
– Items added.
– Items deleted.
Objects First with Java - A Practical Introduction using BlueJ, © David J. Barnes,
Michael Kölling
For-each Loops & ArrayLists
• Simplifies repetitive processing of items in a collection
• Can be applied to a collection of items, such as ArrayList:
ArrayList<Book> list = new ArrayList<Book>();
• We can add items to the list:
list.add(new Book(“Ender’s Game”,
“Orson Scott Card”));
• The following loop will print each book:
for (Book myBook : list)
System.out.println (myBook);
Adding a Transaction class
9. Create a Transaction class & enumerated type:
* You can use Eclipse’s source code generation to
create getters and setters for the fields
10.Create an ArrayList field in BankAccount to store a
list of Transactions, & initialize it in the constructor.
Adding a Transaction class, cont’d
11.Update deposit and debit so that they also take a
String description as a parameter, this will
temporarily cause errors in main.
12.Update debit and deposit to to add a new
Transaction whenever balance is changed.
13.Create new deposit and debit methods that only
take amount as a parameter, and simply calls the
existing corresponding debit/deposit method with
an empty string (“”).
13.Create a printSummary method that calls the
print() method and then prints all the transactions
using a for each loop. Test this in main.
Created by Emily Hill & Jerry Alan Fails
Homework
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Finish lab
CodingBat
Look at Project 1
Read Chapter 5
Created by Emily Hill & Jerry Alan Fails