How to empty the JTextField automatically? Please HELP me.

Question

Hello,
This is my full listing program:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;
import javax.swing.event.*;
import javax.swing.border.*;
public class PortGUI extends JFrame
     private     JButton btOk;
     private JButton btCancel;
     private     JButton btReply;
     private     JLabel lblServIP;
     private     JLabel lblAuth;
     private JLabel lblThrd;
     private JLabel lblAcc;
     private JLabel lblMax;
     private JLabel lblAuthent;
     private JLabel lblAdm;
     private JLabel lblReplServ;
     private JCheckBox chkUsers;
     private JCheckBox chkEnbDbg;
     private JOptionPane pnlErr = new JOptionPane();
     public PortGUI()
          // Create main panel
          JPanel topPanel     = new JPanel();
          topPanel.setLayout(null);
          getContentPane().add( topPanel );
     // Create Server Settings panel
          JPanel panelsett = new JPanel();
          panelsett.setLayout(null);
          panelsett.setBounds(5,5,680, 200);
          // panelsett containers
          final JTextField fldServIP = new JTextField();
          fldServIP.setBounds( 160, 30, 100, 25 );
          fldServIP.setFocusAccelerator( 'v' );
          panelsett.add(fldServIP);
          lblServIP = new JLabel( "Server IP"     );
          lblServIP.setBounds( 20, 30, 100, 25 );
          lblServIP.setLabelFor(     fldServIP );
          panelsett.add(lblServIP);
          final JTextField fldAuth = new JTextField();
          fldAuth.setBounds( 600, 30, 50, 25 );
          fldAuth.setFocusAccelerator( 'v' );
          panelsett.add(fldAuth);
          lblAuth = new JLabel( "Incoming Radius Authentication Port");
          lblAuth.setBounds( 350, 30, 300, 25 );
          lblAuth.setLabelFor(fldAuth);
          panelsett.add(lblAuth);                                        
          final JTextField fldThrd =     new     JTextField();
          fldThrd.setBounds( 160, 60, 50, 25 );
          fldThrd.setFocusAccelerator( 'a' );
          panelsett.add(fldThrd);
          lblThrd = new JLabel( "Worker Threads" );
          lblThrd.setBounds( 20, 60, 100, 25 );
          lblThrd.setLabelFor(fldThrd);
          panelsett.add(lblThrd);
          final JTextField fldAcc =     new     JTextField();
          fldAcc.setBounds( 600, 60, 50, 25 );
          fldAcc.setFocusAccelerator( 'a' );
          panelsett.add( fldAcc );
          lblAcc = new JLabel( "Incoming Radius Accounting Port" );
          lblAcc.setBounds( 350, 60, 300, 25 );
          lblAcc.setLabelFor(     fldAcc );
          panelsett.add( lblAcc );
          final JTextField fldMax =     new     JTextField();
          fldMax.setBounds( 160, 90, 50, 25 );
          fldMax.setFocusAccelerator( 'c' );
          panelsett.add( fldMax );
          lblMax = new JLabel( "Maximum Consoles" );
          lblMax.setBounds( 20, 90, 200, 25 );
          lblMax.setLabelFor(     fldMax );
          panelsett.add(lblMax);
          // Create combo box
          String[] AuthStrings = {"Local Server", "Proxy Server", "Local and Proxy"};
          JComboBox AuthList = new JComboBox(AuthStrings);
          AuthList.setSelectedIndex(2);
          AuthList.setSelectedItem(null);
          AuthList.setBounds(450, 90, 200, 25);
          panelsett.add(AuthList);          
          lblAuthent = new JLabel( "Authenticator" );
          lblAuthent.setBounds( 350, 90, 100, 25 );
          lblAuthent.setLabelFor(     AuthList);
          panelsett.add(lblAuthent);
          final JTextField fldAdm =     new     JTextField();
          fldAdm.setBounds( 160, 120, 50, 25 );
          fldAdm.setFocusAccelerator( 'c' );
          panelsett.add( fldAdm );
          lblAdm = new JLabel( "Admin TCP Port" );
          lblAdm.setBounds( 20, 120, 150, 25 );
          lblAdm.setLabelFor(     fldAdm );
          panelsett.add(lblAdm);
          // create checkbox
          chkUsers = new JCheckBox("Cache Users in Memory");
          chkUsers.setBounds(350, 120, 250, 25);
chkUsers.setMnemonic('m');
chkUsers.setSelected(false);
panelsett.add(chkUsers);
          final JTextField fldReplServ =     new     JTextField();
          fldReplServ.setBounds( 160, 150, 100, 25 );
          fldReplServ.setFocusAccelerator( 'c' );
          panelsett.add( fldReplServ );
          lblReplServ = new JLabel( "Replication Server IP" );
          lblReplServ.setBounds( 20, 150, 200, 25 );
          lblReplServ.setLabelFor(fldReplServ);
          panelsett.add(lblReplServ);
          chkEnbDbg = new JCheckBox("Enable Debug Trace Output");
chkEnbDbg.setBounds(350, 150, 250, 25);
chkEnbDbg.setMnemonic('n');
chkEnbDbg.setSelected(false);
panelsett.add(chkEnbDbg);
          Border etched;
          etched = BorderFactory.createLoweredBevelBorder();
     TitledBorder title;
     title = BorderFactory.createTitledBorder(etched, "Server Settings");
title.setTitleJustification(TitledBorder.LEFT);
panelsett.setBorder(title);
topPanel.add(panelsett);
          // Create a button
          btOk = new JButton( "OK" );
          btOk.setBorder(BorderFactory.createRaisedBevelBorder());
          btOk.setBounds( 170, 270, 100, 35 );
          btOk.setEnabled(false );
          topPanel.add(btOk);
          btReply = new JButton( "Apply" );
          btReply.setBorder(BorderFactory.createRaisedBevelBorder());
          btReply.setBounds( 300, 270, 100, 35 );
          topPanel.add(btReply);
          btCancel = new JButton( "Cancel" );
          btCancel.setBorder(BorderFactory.createRaisedBevelBorder());
          btCancel.setBounds( 420, 270, 100, 35 );
          btCancel.addActionListener(new ActionListener()
public void actionPerformed(ActionEvent e)
     System.exit(0);
          topPanel.add(btCancel);
          // Action for each components
          fldServIP.getDocument().addDocumentListener(new DocumentListener()
               public void     insertUpdate( DocumentEvent event )
                    String     sString     = fldServIP.getText();
                    try     
                         int     iValue = Integer.parseInt( sString );
                         btOk.setEnabled( true );
                    catch( NumberFormatException e )
                         if(     fldServIP.getText().length() == 4 )
               JOptionPane.showMessageDialog(pnlErr,
"Please try again",
"Error Message",
JOptionPane.ERROR_MESSAGE);
public void removeUpdate( DocumentEvent event )
     // Prevent the user     from entering a blank field
     if(     fldServIP.getText().length() == 0 )
     btOk.setEnabled( false );
     else
          // Do the same error checking as insertUpdate()
          insertUpdate( event );
public void changedUpdate( DocumentEvent event )
     // Nothing to do here
          fldAuth.getDocument().addDocumentListener(new DocumentListener()
               public void     insertUpdate( DocumentEvent event )
                    String     sString     = fldAuth.getText();
                    try     
                         int     iValue = Integer.parseInt( sString );
                         btOk.setEnabled( true );
                    catch( NumberFormatException e )
                         if(     fldAuth.getText().length() == 4 )
               JOptionPane.showMessageDialog(pnlErr,
"Please try again",
"Error Message",
JOptionPane.ERROR_MESSAGE);
public void removeUpdate( DocumentEvent event )
     // Prevent the user     from entering a blank field
     if(     fldAuth.getText().length() == 0 )
     btOk.setEnabled( false );
     else
          // Do the same error checking as insertUpdate()
          insertUpdate( event );
public void changedUpdate( DocumentEvent event )
     // Nothing to do here
     fldThrd.getDocument().addDocumentListener(new DocumentListener()
               public void     insertUpdate( DocumentEvent event )
                    String     sString     = fldThrd.getText();
                    try     
                         int     iValue = Integer.parseInt( sString );
                         btOk.setEnabled( true );
                    catch( NumberFormatException e )
                         if(     fldThrd.getText().length() == 4 )
               JOptionPane.showMessageDialog(pnlErr,
"Please try again",
"Error Message",
JOptionPane.ERROR_MESSAGE);
public void removeUpdate( DocumentEvent event )
     // Prevent the user     from entering a blank field
     if(     fldThrd.getText().length() == 0 )
     btOk.setEnabled( false );
     else
          // Do the same error checking as insertUpdate()
          insertUpdate( event );
public void changedUpdate( DocumentEvent event )
     // Nothing to do here
fldAcc.getDocument().addDocumentListener(new DocumentListener()
               public void     insertUpdate( DocumentEvent event )
                    String     sString     = fldAcc.getText();
                    try     
                         int     iValue = Integer.parseInt( sString );
                         btOk.setEnabled( true );
                    catch( NumberFormatException e )
                         if(     fldAcc.getText().length() == 4 )
               JOptionPane.showMessageDialog(pnlErr,
"Please try again",
"Error Message",
JOptionPane.ERROR_MESSAGE);
public void removeUpdate( DocumentEvent event )
     // Prevent the user     from entering a blank field
     if(     fldAcc.getText().length() == 0 )
     btOk.setEnabled( false );
     else
          // Do the same error checking as insertUpdate()
          insertUpdate( event );
public void changedUpdate( DocumentEvent event )
     // Nothing to do here
fldMax.getDocument().addDocumentListener(new DocumentListener()
               public void     insertUpdate( DocumentEvent event )
                    String     sString     = fldMax.getText();
                    try     
                         int     iValue = Integer.parseInt( sString );
                         btOk.setEnabled( true );
                    catch( NumberFormatException e )
                         if(     fldMax.getText().length() == 4 )
               JOptionPane.showMessageDialog(pnlErr,
"Please try again",
"Error Message",
JOptionPane.ERROR_MESSAGE);
public void removeUpdate( DocumentEvent event )
     // Prevent the user     from entering a blank field
     if(     fldMax.getText().length() == 0 )
     btOk.setEnabled( false );
     else
          // Do the same error checking as insertUpdate()
          insertUpdate( event );
public void changedUpdate( DocumentEvent event )
     // Nothing to do here
fldAdm.getDocument().addDocumentListener(new DocumentListener()
               public void     insertUpdate( DocumentEvent event )
                    String     sString     = fldAdm.getText();
                    try     
                         int     iValue = Integer.parseInt( sString );
                         btOk.setEnabled( true );
                    catch( NumberFormatException e )
                         if(     fldAdm.getText().length() == 4 )
               JOptionPane.showMessageDialog(pnlErr,
"Please try again",
"Error Message",
JOptionPane.ERROR_MESSAGE);
public void removeUpdate( DocumentEvent event )
     // Prevent the user     from entering a blank field
     if(     fldAdm.getText().length() == 0 )
     btOk.setEnabled( false );
     else
          // Do the same error checking as insertUpdate()
          insertUpdate( event );
public void changedUpdate( DocumentEvent event )
     // Nothing to do here
fldReplServ.getDocument().addDocumentListener(new DocumentListener()
               public void     insertUpdate( DocumentEvent event )
                    String     sString     = fldReplServ.getText();
                    try     
                         int     iValue = Integer.parseInt( sString );
                         btOk.setEnabled( true );
                    catch( NumberFormatException e )
                         if(     fldReplServ.getText().length() == 4 )
               JOptionPane.showMessageDialog(pnlErr,
"Please try again",
"Error Message",
JOptionPane.ERROR_MESSAGE);
public void removeUpdate( DocumentEvent event )
     // Prevent the user     from entering a blank field
     if(     fldReplServ.getText().length() == 0 )
     btOk.setEnabled( false );
     else
          // Do the same error checking as insertUpdate()
          insertUpdate( event );
public void changedUpdate( DocumentEvent event )
     // Nothing to do here
     public static void main(String[] args)
          //int windowWidth, windowHeight;
          int windowWidth = 700;
int windowHeight = 400;
          PortGUI window = new PortGUI();
          window.setTitle("");
          Dimension windowSize = window.getSize();
          Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
          window.setSize(windowWidth, windowHeight);
          window.setLocation((screenSize.width - windowWidth) / 2, (screenSize.height - windowHeight) / 2);
          window.setVisible(true);
          window.setResizable(false);
On that listing program, my problem is in field document listener, that is:
fldThrd.getDocument().addDocumentListener(new DocumentListener()
               public void     insertUpdate( DocumentEvent event )
                    String     sString     = fldThrd.getText();
                    try     
                         int     iValue = Integer.parseInt( sString );
                         btOk.setEnabled( true );
                    catch( NumberFormatException e )
                         if(     fldThrd.getText().length() == 4 )
               JOptionPane.showMessageDialog(pnlErr,
"Please try again",
"Error Message",
JOptionPane.ERROR_MESSAGE);
if I execute this program, the textfield can only receive integer input. If input is string til 4 times, the dialog panel will display error message. After that, textfield must be empty (delete automatically).
I want to ask you about how I can emptying that textfield automatically after the dialog panel is appear?
Please help me to get out from my problem.
Thank's for your help,
har

Answer 1

Hi,
To empty the text file, use the method setText("").
eg. fldServIP.setText("");
fldServIP is one of your textfield. So whereever you are showing the dialog box, use setText("") for the corresponding textfields.
All the best