Writing Data to a Sequential Data File - Java Programming: Comprehensive Concepts and Techniques - page 513

Writing Data in the BillPayer Program

Figure 8-25 displays the actionPerformed() method. Line 173 calls a method
named checkFields(), which will be coded later in this chapter. If the checkFields()
method returns a true value, the program writes the data to the data file (lines 176
through 184). The Box 4 message box from Table 8-2 on page 491 is coded in line
186. If an error occurs during the write process, the system exits with an error code
of 1 in line 190, and the data file closes automatically. The try and catch structure
ensures that all errors are handled by the program as required by Java.

169 public void actionPerformed ( ActionEvent e )

170 {

171 String arg = e.getActionCommand () ;

172
173 if ( checkFields ())

174 {

175 try

176 {

177 output.writeUTF ( acctNum.getText ()) ;

178 output.writeUTF ( pmt.getText ()) ;

179 output.writeUTF ( firstName.getText ()) ;

180 output.writeUTF ( lastName.getText ()) ;

181 output.writeUTF ( address.getText ()) ;

182 output.writeUTF ( city.getText ()) ;

183 output.writeUTF ( state.getText ()) ;

184 output.writeUTF ( zip.getText ()) ;

185
186 JOptionPane.showMessageDialog ( null , "The payment information has been saved." ,

"Submission Successful" ,JOptionPane.INFORMATION_MESSAGE ) ;

187 }

188 catch ( IOException c )

189 {

190 System .exit ( 1 ) ;

191 }

192 clearFields () ;

193 }

194 }

FIGURE 8-25

The following step codes the actionPerformed() method.

To Code the actionPerformed() Method

1. Enter lines 171
through 193 as
shown in
Figure 8-25.
TextPad displays
the new code
(Figure 8-26). The
action event writes
the data to the
data file when the
user clicks the
Submit button.

writeUTF()
methods

code to exit program

FIGURE 8-26

code to display
message box