Writing Data to a Sequential Data File - Java Programming: Comprehensive Concepts and Techniques - page 499

Adding Components to the Interface
Adding components to the BillPayer interface involves the following:
(1) constructing the components, (2) implementing layout managers for place-
ment, and (3) using the add() methods to insert the components into the JFrame.
The components in the BillPayer interface include the JFrame, which already was
created; the content pane to hold all of the components; JLabels to hold words,
instructions, or prompts; JTextFields to allow for user data entry; JButtons to add
functionality to the interface; and JPanels to assist with component placement.
You may remember that JPanels and JFrames are special containers that house
other components, such as user-interface controls and other containers.

Constructing the Components

Figure 8-12 displays the constructors for the BillPayer interface and the
declaration of the variable to hold the DataOutputStream. Eight JPanel contain-
ers are created in lines 21 through 28. Recall from the storyboard in Figure 8-3
on page 490 that each row of JLabels and JTextFields will be placed in its own
panel. Then, in line 31, a larger panel, named fieldPanel, will contain all of the
rows. Finally, line 32 constructs the buttonPanel.

15 public class BillPayer extends JFrame implements ActionListener
16 {
17 //Declare output stream

18 DataOutputStream output;

19
20 //Construct a panel for each row

21 JPanel firstRow = new JPanel () ;

22 JPanel secondRow = new JPanel () ;

23 JPanel thirdRow = new JPanel () ;

24 JPanel fourthRow = new JPanel () ;

25 JPanel fifthRow = new JPanel () ;

26 JPanel sixthRow = new JPanel () ;

27 JPanel seventhRow = new JPanel () ;

28 JPanel eighthRow = new JPanel () ;

29
30 //Construct a panel for the fields and buttons

31 JPanel fieldPanel = new JPanel () ;

32 JPanel buttonPanel = new JPanel () ;

33
34 //Construct labels and text boxes

35 JLabel acctNumLabel = new JLabel ( "Account Number: " ) ;

36 JTextField acctNum = new JTextField ( 15 ) ;

37 JLabel pmtLabel = new JLabel ( "Payment Amount:" ) ;

38 JTextField pmt = new JTextField ( 10 ) ;

39 JLabel firstNameLabel = new JLabel ( "First Name: " ) ;

40 JTextField firstName = new JTextField ( 10 ) ;

41 JLabel lastNameLabel = new JLabel ( "Last Name:" ) ;

42 JTextField lastName = new JTextField ( 20 ) ;

43 JLabel addressLabel = new JLabel ( "Address:" ) ;

44 JTextField address = new JTextField ( 35 ) ;

45 JLabel cityLabel = new JLabel ( "City: " ) ;

46 JTextField city = new JTextField ( 10 ) ;

47 JLabel stateLabel = new JLabel ( "State:" ) ;

48 JTextField state = new JTextField ( 2 ) ;

49 JLabel zipLabel = new JLabel ( "Zip:" ) ;

50 JTextField zip = new JTextField ( 9 ) ;

51
52 //Construct button

53 JButton submitButton = new JButton ( "Submit" ) ;

54
55 public static void main ( String [] args )

FIGURE 8-12