Why do I get Illegal Component position when I say FlowLayout.CENTER

Question

The code runs fine if you replace the line
Jp7.add(submitButton, FlowLayout.CENTER);
with
Jp7.add(submitButton);
I know FlowLayout's default location is CENTER. But when I explicitly say to center the button, it crashes during runtime but compiles fine.
Whats the reason for this? Is this a bug?
I am using 1.4.0_03.
I getthe following error.
Exception in thread "main" java.lang.IllegalArgumentException: illegal component
position
at java.awt.Container.addImpl(Container.java:568)
at java.awt.Container.add(Container.java:327)
at Mon2.main(Mon2.java:114)
ALSO CAN I DO THE SAME WITHOUT USING SO MANY JPANELS?????????????????? I AM NOT NEW TO PROGRAMMING BUT I AM NEW TO GUI PROGRAMMING.
Thanks in advance.
import java.sql.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class Mon2 extends JFrame{
static long i =0;
static int jobid = 0;
static String StartTime = "";
static String LastReport = "";
static String FinishTime = "";
static String Description = "";
static String job_position = "";
static String desc ="";
public static String database = "";
public static String user = "";
public static String password = "";
static int counter = 1;
static boolean valuesEntered = false;
  JButton jButton1 = new JButton();
  JButton jButton2 = new JButton();
  JButton jButton3 = new JButton();
  BorderLayout borderLayout1 = new BorderLayout();
  JLabel jLabel1 = new JLabel();
JTextPane jTextArea1 = new JTextPane();
static JTextField userArea = new JTextField();
static JPasswordField passArea = new JPasswordField();
static JTextField databaseArea = new JTextField();     
static JFrame f = new JFrame();
static JLabel us = new JLabel ("UserName: ");
static JLabel pa = new JLabel ("Password: ");
static JLabel da = new JLabel ("Database: ");
  BorderLayout borderLayout2 = new BorderLayout();
  JPanel jPanel1 = new JPanel();
  JLabel jLabel2 = new JLabel();
     public Mon2() {
    try  {
      jbInit();
    catch (Exception e) {
      e.printStackTrace();
     public static void main(String args[]) {
          System.out.println("Starting Mon2...");
    f.setSize(300,200);
    f.setTitle("Login");
    f.setLocation(250,250);
    f.setResizable(false);
    Panel Jp1 = new Panel (new BorderLayout());
    Panel Jp3 = new Panel (new BorderLayout());
    Jp3.add(us, BorderLayout.NORTH);
    Jp3.add(pa, BorderLayout.CENTER);
    Jp3.add(da, BorderLayout.SOUTH);
    userArea.setEditable(true);
    userArea.setSize(20,20);
    passArea.setEditable(true);
    databaseArea.setEditable(true);
    JButton submitButton = new JButton("Submit");
    JPanel Jp2 = new JPanel (new BorderLayout());
    JPanel Jp4 = new JPanel (new FlowLayout());
    userArea.setPreferredSize(new Dimension(200,21));
    Jp4.add(userArea, FlowLayout.LEFT);
    Jp4.add(us, FlowLayout.LEFT);
    JPanel Jp5 = new JPanel (new FlowLayout());
    passArea.setPreferredSize(new Dimension(200,21));
    Jp5.add(passArea,FlowLayout.LEFT);
    Jp5.add(pa, FlowLayout.LEFT);
    JPanel Jp6 = new JPanel (new FlowLayout());
    databaseArea.setPreferredSize(new Dimension(200,21));
    databaseArea.setText("DWPROD");
    Jp6.add(databaseArea,FlowLayout.LEFT);
    Jp6.add(da, FlowLayout.LEFT);
    Jp1.add(Jp4, BorderLayout.NORTH);
    Jp1.add(Jp5, BorderLayout.CENTER);
    Jp2.add(Jp6, BorderLayout.NORTH);
   JPanel Jp7 = new JPanel(new FlowLayout());
///////////////////////////This is  the line//////////////////
//If you remove the ,FlowLayout.CENTER it works fine.
//If you leave it like as it is, it will compile but then give runtime error
    Jp7.add(submitButton, FlowLayout.CENTER);
    Jp2.add(Jp7, BorderLayout.SOUTH);
    Jp1.add(Jp2, BorderLayout.SOUTH);
    f.getContentPane().add(Jp1);
    Image img = Toolkit.getDefaultToolkit().getImage("c:\\appletHeader.gif");
    f.setIconImage(img);
    f.setDefaultCloseOperation(3);
    f.setVisible(true);
    f.pack();
     submitButton.resize(75, 30);
    submitButton.addActionListener(new java.awt.event.ActionListener() {
    public void actionPerformed(ActionEvent e) {
    user = userArea.getText();
    password = passArea.getText();
    database = databaseArea.getText();
    if((user.equals(null) || password.equals(null) || database.equals(null) || user.equals("") || password.equals("") || database.equals(""))){
    valuesEntered = false;
    else{
         valuesEntered = true;
    if(valuesEntered == true){
    f.setVisible(false);
          Mon2 mainFrame = new Mon2();
          mainFrame.setSize(600, 400);
          mainFrame.setTitle("Monitor");
    mainFrame.setLocation(100,200);
    mainFrame.setResizable(false);
    desc = "ERROR! or there are no locked jobs.";
          mainFrame.setVisible(true);
    else{
    JOptionPane.showMessageDialog(null,"Must enter values for UserName, Password and Database", "Value Required",JOptionPane.INFORMATION_MESSAGE);
//    System.exit(0);
  private void jbInit() throws Exception {
    this.setDefaultCloseOperation(3);
    jButton1.setText("Refresh");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
      jButton1_actionPerformed(e);
    jButton2.setText(" Exit ");
    jButton2.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        System.exit(0);
    this.getContentPane().setLayout(borderLayout1);
    jButton3.setText("Clear");
    jButton3.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        jTextArea1.setText("Click on Refresh to update screen.");
    Panel p = new Panel(new FlowLayout());
    Panel p2 = new Panel (new BorderLayout());
    jLabel1.setText("Monitor for current Job");
    jTextArea1.setPreferredSize(new Dimension(8, 50));
    jTextArea1.setContentType("text/html");
    jTextArea1.setText("");
    jTextArea1.setEditable(false);
    f.setResizable(false);
    f.setTitle("Login");
    jLabel2.setHorizontalTextPosition(SwingConstants.LEFT);
    jLabel2.setText("jLabel2");
    jLabel2.setHorizontalAlignment(SwingConstants.LEFT);
    f.getContentPane().setLayout(borderLayout2);
    jTextArea1.setSize(100,10);
    p.add(jButton1);
    p.add(jButton3);
    p.add(jButton2);
    this.getContentPane().add(jLabel1, BorderLayout.NORTH);
    this.getContentPane().add(jTextArea1, BorderLayout.CENTER);
    p2.add(p, BorderLayout.CENTER);
    this.getContentPane().add(p2, BorderLayout.SOUTH);
    pack();
    f.getContentPane().add(jPanel1, BorderLayout.CENTER);
    jPanel1.add(jLabel2, null);
  void jButton1_actionPerformed(ActionEvent e){
        jTextArea1.setText("Refreshing...");
        long i = 0;
     try{
          jTextArea1.setText("In side try block");
                Thread.sleep(1000);
               DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
               jTextArea1.setText("DriverManager");
              Connection conn=
               DriverManager.getConnection("jdbc:oracle:thin:@machine:1234:"+ database, user, password);
                                                                      jTextArea1.setText("Got COnnection");
               Statement stmt = conn.createStatement();
               jTextArea1.setText("Statement Created");
               ResultSet rs =
               stmt.executeQuery("select 1, sysdate, sysdate, sysdate, sysdate, sysdate from dual ");
               jTextArea1.setText("Query Executed");
               while(rs.next()){
      jobid = rs.getInt(1);
      StartTime = rs.getString(2);
      LastReport = rs.getString(3);
      FinishTime = rs.getString(4);
      Description = rs.getString(5);
      job_position = rs.getString(6);
      desc = "<b>Count: </b>" + counter + "" +
                 "<p><table border = '1'><tr><td><b>JOB ID:      </b></td><td>" + jobid + "</td></tr>" +
             "<tr><td><b>Start Time:  </b></td><td>" + StartTime + "</td></tr>" +
             "<tr><td><b>Last Report: </b></td><td>" + LastReport + "</td></tr>" +
             "<tr><td><b>FinishTime:  </b></td><td>" + FinishTime + "</td></tr>" +
             "<tr><td><b>Description: </b></td><td>" + Description + "</td></tr>" +
             "<tr><td><b>Position:    </b></td><td>" + job_position + "</td></tr></table>";
              counter = counter + 1;
                 rs.close();
               conn.close();
                jTextArea1.setText("Sleeping");
                jTextArea1.setText(desc);
                desc = "";
          catch (SQLException se){
          jTextArea1.setText(desc + se);
       catch(Exception ee){
            jTextArea1.setText("Exception occured\n\n" + ee);
}

Answer 1

Get your basics checked.
Go to:
http://developer.java.sun.com/developer/onlineTraining/GUI/AWTLayoutMgr/shortcourse.html#whatAreLMs
And find the heading: FlowLayout Variations
FlowLayout can be customized at construction time by passing the
constructor an alignment setting:
FlowLayout.CENTER (the default)
FlowLayout.RIGHT
FlowLayout.LEFT