// Fig. 17.8: CreateSequentialFile.java
// Writing objecst sequentially to a file with class ObjectOutputStream.
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

import com.deitel.jhtp5.ch17.BankUI;
import com.deitel.jhtp5.ch17.AccountRecord;

public class CreateSequentialFile extends JFrame {
   private ObjectOutputStream output;
   private BankUI userInterface;
   private JButton enterButton, openButton;

   // set up GUI
   public CreateSequentialFile()
   {
      super( "Creating a Sequential File of Objects" );

      // create instance of reusable user interface
      userInterface = new BankUI( 4 );  // four textfields
      getContentPane().add( userInterface, BorderLayout.CENTER );
      
      // configure button doTask1 for use in this program
      openButton = userInterface.getDoTask1Button();
      openButton.setText( "Save into File ..." );

      // register listener to call openFile when button pressed
      openButton.addActionListener(

         // anonymous inner class to handle openButton event
         new ActionListener() {

            // call openFile when button pressed
            public void actionPerformed( ActionEvent event )
            {
               openFile();
            }

         } // end anonymous inner class

      ); // end call to addActionListener

      // configure button doTask2 for use in this program
      enterButton = userInterface.getDoTask2Button();
      enterButton.setText( "Enter" );
      enterButton.setEnabled( false );  // disable button

      // register listener to call addRecord when button pressed
      enterButton.addActionListener(

         // anonymous inner class to handle enterButton event
         new ActionListener() {

            // call addRecord when button pressed
            public void actionPerformed( ActionEvent event )
            {
               addRecord();
            }

         } // end anonymous inner class

      ); // end call to addActionListener

      // register window listener to handle window closing event
      addWindowListener(

         // anonymous inner class to handle windowClosing event
         new WindowAdapter() {

            // add current record in GUI to file, then close file
            public void windowClosing( WindowEvent event )
            {
               if ( output != null )
                  addRecord();

               closeFile();
            }

         } // end anonymous inner class

      ); // end call to addWindowListener

      setSize( 300, 200 );
      setVisible( true );

   } // end CreateSequentialFile constructor

   // allow user to specify file name
   private void openFile()
   {
      // display file dialog, so user can choose file to open
      JFileChooser fileChooser = new JFileChooser();
      fileChooser.setFileSelectionMode( JFileChooser.FILES_ONLY );
      
      int result = fileChooser.showSaveDialog( this );

      // if user clicked Cancel button on dialog, return
      if ( result == JFileChooser.CANCEL_OPTION )
         return;

      File fileName = fileChooser.getSelectedFile(); // get selected file
      
      // display error if invalid 
      if ( fileName == null || fileName.getName().equals( "" ) )
         JOptionPane.showMessageDialog( this, "Invalid File Name", 
            "Invalid File Name", JOptionPane.ERROR_MESSAGE );

      else {

         // open file
         try {
            output = new ObjectOutputStream(
               new FileOutputStream( fileName ) );

            openButton.setEnabled( false );
            enterButton.setEnabled( true );
         }

         // process exceptions from opening file
         catch ( IOException ioException ) {
            JOptionPane.showMessageDialog( this, "Error Opening File", 
               "Error", JOptionPane.ERROR_MESSAGE );
         }  
         
      } // end else
  
   } // end method openFile

   // close file and terminate application 
   private void closeFile() 
   {
      // close file 
      try {
         output.close();
         System.exit( 0 );
      }

      // process exceptions from closing file 
      catch( IOException ioException ) {
         JOptionPane.showMessageDialog( this, "Error closing file", 
            "Error", JOptionPane.ERROR_MESSAGE );
         System.exit( 1 );
      }

   } // end method closeFile

   // add record to file
   public void addRecord()
   {
      int accountNumber = 0;
      AccountRecord record;
      String fieldValues[] = userInterface.getFieldValues();
     
      // if account field value is not empty
      if ( ! fieldValues[ BankUI.ACCOUNT ].equals( "" ) ) {

         // output values to file
         try {
            accountNumber = Integer.parseInt(
               fieldValues[ BankUI.ACCOUNT ] );

            if ( accountNumber > 0 ) {

               // create new record
               record = new AccountRecord( accountNumber,
                  fieldValues[ BankUI.FIRSTNAME ],
                  fieldValues[ BankUI.LASTNAME ],
                  Double.parseDouble( fieldValues[ BankUI.BALANCE ] ) );

               // output record and flush buffer
               output.writeObject( record );
               output.flush();
            }
            else
            {
                JOptionPane.showMessageDialog( this,
                   "Account number must be greater than 0",
                   "Bad account number", JOptionPane.ERROR_MESSAGE );
            }

            // clear textfields
            userInterface.clearFields();

         } // end try

         // process invalid account number or balance format
         catch ( NumberFormatException formatException ) {
            JOptionPane.showMessageDialog( this,
               "Bad account number or balance", "Invalid Number Format",
               JOptionPane.ERROR_MESSAGE );
         }

         // process exceptions from file output
         catch ( IOException ioException ) {
             JOptionPane.showMessageDialog( this, "Error writing to file",
                "IO Exception", JOptionPane.ERROR_MESSAGE );
            closeFile();
         }

      } // end if

   } // end method addRecord

   public static void main( String args[] )
   {
      new CreateSequentialFile();
   }

} // end class CreateSequentialFile

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 * (C) Copyright 1992-2003 by Deitel & Associates, Inc. and               *
 * Prentice Hall. All Rights Reserved.                                    *
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