Help Pls!! Jcombobox populate with mysql

[kwink]

Hi guys! need help, I don't know how to populate my combobox linking it to mysql.. i've read alot of topics regarding this but i still couldn't get it.. Im a slow learner and a beginner in Java. I'm using netbeans.
if there is no way of linking my combobox to mysql, could anyone pls tell me how to save the items i added in the combobox even when I close the window. cause when I run the program, whenever I close the window or end the program the items added in my combobox would be gone.. (the letters in color red in my code is the one)T_T HELP!!! :confused:
this is my code..

/*
* MainClass.java
*
* Created on March 13, 2009, 3:37 PM
*/

/**
*
* @author windemuy
*/
import java.sql.*;
import javax.swing.*;
import javax.swing.table.*;
import java.awt.*;

public class MainClass extends javax.swing.JFrame {

/** Creates new form MainClass */
public MainClass() {
initComponents();
}

/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
// <editor-fold defaultstate="collapsed" desc=" Generated Code ">
private void initComponents() {
jLabel1 = new javax.swing.JLabel();
jTabbedPane1 = new javax.swing.JTabbedPane();
jPanel1 = new javax.swing.JPanel();
jTabbedPane4 = new javax.swing.JTabbedPane();
jPanel2 = new javax.swing.JPanel();
jLabel2 = new javax.swing.JLabel();
txtname = new javax.swing.JTextField();
jLabel3 = new javax.swing.JLabel();
address = new javax.swing.JTextField();
jLabel4 = new javax.swing.JLabel();
txtcontact = new javax.swing.JTextField();
cbobook = new javax.swing.JComboBox();
jLabel5 = new javax.swing.JLabel();
jLabel6 = new javax.swing.JLabel();
txtremarks = new javax.swing.JTextField();
jLabel7 = new javax.swing.JLabel();
txtpayment = new javax.swing.JTextField();
jButton1 = new javax.swing.JButton();
jLabel11 = new javax.swing.JLabel();
txtid = new javax.swing.JTextField();
jLabel12 = new javax.swing.JLabel();
txtprice = new javax.swing.JTextField();
txtchange = new javax.swing.JTextField();
jButton5 = new javax.swing.JButton();
jPanel3 = new javax.swing.JPanel();
jLabel8 = new javax.swing.JLabel();
txtadd = new javax.swing.JTextField();
jLabel9 = new javax.swing.JLabel();
txtremove = new javax.swing.JTextField();
jButton2 = new javax.swing.JButton();
jButton3 = new javax.swing.JButton();
jLabel10 = new javax.swing.JLabel();
num = new javax.swing.JTextField();
jPanel5 = new javax.swing.JPanel();
jScrollPane1 = new javax.swing.JScrollPane();
jTable1 = new javax.swing.JTable();
jButton4 = new javax.swing.JButton();
jButton6 = new javax.swing.JButton();
jPanel6 = new javax.swing.JPanel();
jLabel13 = new javax.swing.JLabel();
txtname1 = new javax.swing.JTextField();
jLabel14 = new javax.swing.JLabel();
address1 = new javax.swing.JTextField();
jLabel15 = new javax.swing.JLabel();
txtcontact1 = new javax.swing.JTextField();
cbobook1 = new javax.swing.JComboBox();
jLabel16 = new javax.swing.JLabel();
jLabel17 = new javax.swing.JLabel();
txtremarks1 = new javax.swing.JTextField();
jLabel18 = new javax.swing.JLabel();
txtpayment1 = new javax.swing.JTextField();
jButton7 = new javax.swing.JButton();
jLabel19 = new javax.swing.JLabel();
txtid1 = new javax.swing.JTextField();
jLabel20 = new javax.swing.JLabel();
txtprice1 = new javax.swing.JTextField();
txtchange1 = new javax.swing.JTextField();
jButton8 = new javax.swing.JButton();

getContentPane().setLayout(null);

setDefaultCloseOperation(javax.swing.WindowConstan ts.EXIT_ON_CLOSE);
setTitle("Winde's Book Shop");
addWindowListener(new java.awt.event.WindowAdapter() {
public void windowOpened(java.awt.event.WindowEvent evt) {
window(evt);
}
});

jLabel1.setText("Winde's Book Shop");
getContentPane().add(jLabel1);
jLabel1.setBounds(250, 30, 140, 14);

jPanel1.setLayout(null);

jTabbedPane4.setTabPlacement(javax.swing.JTabbedPa ne.BOTTOM);
jPanel2.setLayout(null);

jLabel2.setText("Name:");
jPanel2.add(jLabel2);
jLabel2.setBounds(30, 80, 60, 20);

jPanel2.add(txtname);
txtname.setBounds(100, 80, 380, 20);

jLabel3.setText("Address:");
jPanel2.add(jLabel3);
jLabel3.setBounds(30, 110, 60, 14);

jPanel2.add(address);
address.setBounds(100, 110, 380, 20);

jLabel4.setText("Contact:");
jPanel2.add(jLabel4);
jLabel4.setBounds(30, 140, 60, 14);

jPanel2.add(txtcontact);
txtcontact.setBounds(100, 140, 380, 20);

jPanel2.add(cbobook);
cbobook.setBounds(100, 190, 380, 22);

jLabel5.setText("Book Title");
jPanel2.add(jLabel5);
jLabel5.setBounds(30, 200, 60, 14);

jLabel6.setText("Remarks");
jPanel2.add(jLabel6);
jLabel6.setBounds(30, 240, 100, 14);

jPanel2.add(txtremarks);
txtremarks.setBounds(100, 240, 380, 20);

jLabel7.setText("Payment:");
jPanel2.add(jLabel7);
jLabel7.setBounds(270, 280, 60, 14);

jPanel2.add(txtpayment);
txtpayment.setBounds(340, 280, 80, 20);

jButton1.setText("Submit");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
Submit(evt);
}
});

jPanel2.add(jButton1);
jButton1.setBounds(160, 360, 200, 40);

jLabel11.setText("Customer ID");
jPanel2.add(jLabel11);
jLabel11.setBounds(30, 40, 80, 14);

jPanel2.add(txtid);
txtid.setBounds(100, 30, 70, 30);

jLabel12.setText("Book Price");
jPanel2.add(jLabel12);
jLabel12.setBounds(30, 280, 70, 14);

jPanel2.add(txtprice);
txtprice.setBounds(120, 280, 70, 20);

txtchange.setEditable(false);
jPanel2.add(txtchange);
txtchange.setBounds(340, 310, 80, 20);

jButton5.setText("Change");
jButton5.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
Change(evt);
}
});

jPanel2.add(jButton5);
jButton5.setBounds(240, 310, 90, 23);

jTabbedPane4.addTab("Customer", jPanel2);

jPanel3.setLayout(null);

jLabel8.setText("Add Title");
jPanel3.add(jLabel8);
jLabel8.setBounds(60, 80, 80, 14);

jPanel3.add(txtadd);
txtadd.setBounds(140, 80, 210, 20);

jLabel9.setText("Remove Title");
jPanel3.add(jLabel9);
jLabel9.setBounds(60, 120, 80, 14);

jPanel3.add(txtremove);
txtremove.setBounds(140, 120, 210, 20);

jButton2.setText("Add");
jButton2.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
Add(evt);
}
});

jPanel3.add(jButton2);
jButton2.setBounds(380, 80, 100, 23);

jButton3.setText("Remove");
jButton3.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
Remove(evt);
}
});

jPanel3.add(jButton3);
jButton3.setBounds(380, 120, 100, 23);

jLabel10.setText("Current Books Available:");
jPanel3.add(jLabel10);
jLabel10.setBounds(100, 200, 170, 20);

jPanel3.add(num);
num.setBounds(250, 190, 50, 30);

jTabbedPane4.addTab("Book", jPanel3);

jPanel1.add(jTabbedPane4);
jTabbedPane4.setBounds(30, 20, 520, 440);

jTabbedPane1.addTab("Add +", jPanel1);

jPanel5.setLayout(null);

jTable1.setBackground(new java.awt.Color(255, 204, 153));
jTable1.setModel(new javax.swing.table.DefaultTableModel(
new Object [][] {
{null, null, null, null, null, null, null},
{null, null, null, null, null, null, null},
{null, null, null, null, null, null, null},
{null, null, null, null, null, null, null}
},
new String [] {
"ID", "Name", "Address", "Contact", "Title", "Remarks", "Price"
}
));
jScrollPane1.setViewportView(jTable1);

jPanel5.add(jScrollPane1);
jScrollPane1.setBounds(30, 40, 530, 270);

jButton4.setText("Load Data");
jButton4.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
Load(evt);
}
});

jPanel5.add(jButton4);
jButton4.setBounds(120, 340, 130, 23);

jButton6.setText("Delete");
jButton6.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
Delete(evt);
}
});

jPanel5.add(jButton6);
jButton6.setBounds(350, 340, 100, 23);

jTabbedPane1.addTab("View", jPanel5);

jPanel6.setLayout(null);

jLabel13.setText("Name:");
jPanel6.add(jLabel13);
jLabel13.setBounds(60, 90, 60, 20);

jPanel6.add(txtname1);
txtname1.setBounds(130, 90, 380, 20);

jLabel14.setText("Address:");
jPanel6.add(jLabel14);
jLabel14.setBounds(60, 120, 60, 14);

jPanel6.add(address1);
address1.setBounds(130, 120, 380, 20);

jLabel15.setText("Contact:");
jPanel6.add(jLabel15);
jLabel15.setBounds(60, 150, 60, 14);

jPanel6.add(txtcontact1);
txtcontact1.setBounds(130, 150, 380, 20);

cbobook1.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Harry Potter", "Spiderwick", "Angels & Demons", "Da Vinci Code", "Barbie" }));
jPanel6.add(cbobook1);
cbobook1.setBounds(130, 200, 380, 22);

jLabel16.setText("Book Title");
jPanel6.add(jLabel16);
jLabel16.setBounds(60, 210, 60, 14);

jLabel17.setText("Remarks");
jPanel6.add(jLabel17);
jLabel17.setBounds(60, 250, 100, 14);

jPanel6.add(txtremarks1);
txtremarks1.setBounds(130, 250, 380, 20);

jLabel18.setText("Payment:");
jPanel6.add(jLabel18);
jLabel18.setBounds(300, 290, 60, 14);

jPanel6.add(txtpayment1);
txtpayment1.setBounds(360, 290, 80, 40);

jButton7.setText("Update");
jButton7.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
Update(evt);
}
});

jPanel6.add(jButton7);
jButton7.setBounds(240, 390, 100, 23);

jLabel19.setText("Customer ID");
jPanel6.add(jLabel19);
jLabel19.setBounds(60, 50, 80, 14);

jPanel6.add(txtid1);
txtid1.setBounds(130, 40, 70, 30);

jLabel20.setText("Book Price");
jPanel6.add(jLabel20);
jLabel20.setBounds(60, 290, 70, 14);

jPanel6.add(txtprice1);
txtprice1.setBounds(150, 290, 70, 20);

txtchange1.setEditable(false);
jPanel6.add(txtchange1);
txtchange1.setBounds(150, 330, 70, 20);

jButton8.setText("Change");
jButton8.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
Change2(evt);
}
});

jPanel6.add(jButton8);
jButton8.setBounds(50, 330, 90, 23);

jTabbedPane1.addTab("Update *", jPanel6);

getContentPane().add(jTabbedPane1);
jTabbedPane1.setBounds(20, 60, 580, 510);

pack();
}
// </editor-fold>

private void Update(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
Connection conn = null;
int rows=0;
try{
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost/books_db","root", "root");
Statement s = conn.createStatement();
rows = s.executeUpdate("Update books set Name='"+txtname1.getText() +"',Address='"+address1.getText() +"',Contact='"+
txtcontact1.getText()+"',Title='"+cbobook1.getSele ctedItem()+"',Remarks='"+txtremarks1.getText()+"', Price='"+txtprice1.getText()+"' where ID='"+txtid1.getText()+"'");
conn.close();
}catch(Exception ex){
JOptionPane.showMessageDialog(this,ex.getMessage() );
}

if(rows>0)
JOptionPane.showMessageDialog(this,"Record has been updated");
}

private void Change2(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
int first = Integer.parseInt(txtpayment1.getText());
int second = Integer.parseInt(txtprice1.getText());
int answer = first - second;
txtchange1.setText(" " + answer);
}

private void Submit(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
Connection conn=null;

try {
Class.forName("com.mysql.jdbc.Driver");
conn=DriverManager.getConnection("jdbc:mysql://localhost/books_db","root","root");
Statement st=conn.createStatement();
int rows=st.executeUpdate("Insert into books(ID,Name,Address,Contact,Title,Remarks,Price) " +
" values("+ txtid.getText()+",'"+ txtname.getText()+"','"+ address.getText()+"','"+ txtcontact.getText()+"','"+ cbobook.getSelectedItem()+"','"+ txtremarks.getText()+"','"+ txtprice.getText()+"');");

conn.close();
}catch(Exception ex){

JOptionPane.showMessageDialog(this,ex.getMessage() );

}
}

private void Change(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
int first = Integer.parseInt(txtpayment.getText());
int second = Integer.parseInt(txtprice.getText());
int answer = first - second;
txtchange.setText(" " + answer);
}
//this is the part where i am supposed to populate my combo box.. no codes available in my head... :confused: HELP
private void Add(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
}

private void Remove(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
int index=-1;
try{
index = Integer.parseInt(txtremove.getText());
txtremove.setText("");
cbobook.removeItemAt(index);
} catch (Exception e){
javax.swing.JOptionPane.showMessageDialog(this, e.getMessage());
return;
}
int nitems = cbobook.getItemCount();
num.setText(" " + nitems + "\n");
}

private void Load(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
Connection conn = null;
try{
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost/books_db","root","root");
Statement s=conn.createStatement();
ResultSet rs = s.executeQuery("Select * from books");
DefaultTableModel model = (DefaultTableModel) jTable1.getModel();
model.setNumRows(0);
while (rs.next()){
String []rows = new String[7];
rows[0] = rs.getString("ID");
rows[1] = rs.getString("Name");
rows[2] = rs.getString("Address");
rows[3] = rs.getString("Contact");
rows[4] = rs.getString("Title");
rows[5] = rs.getString("Remarks");
rows[6] = rs.getString("Price");
model.addRow(rows);
}
conn.close();
}catch(Exception e){
JOptionPane.showMessageDialog(this,e.getMessage()) ;
}
}

private void Delete(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
if(jTable1.getSelectedRow()==-1){
JOptionPane.showMessageDialog(this,"Select a row to be deleted.");
return;
}
Connection conn=null;
try{
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost/books_db","root","root");
Statement st = conn.createStatement();
DefaultTableModel model = (DefaultTableModel) jTable1.getModel();
String pid = (String)model.getValueAt(jTable1.getSelectedRow(), 0);
st.executeUpdate("Delete from books where ID =" +pid);
conn.close();
} catch(Exception e){
JOptionPane.showMessageDialog(this, e.getMessage());
}JOptionPane.showMessageDialog(this,"Row deleted, click Load Data to Refresh Table.");
}

private void window(java.awt.event.WindowEvent evt) {
// TODO add your handling code here:
setSize(630,630);
Toolkit toolkit = Toolkit.getDefaultToolkit();
int screenwidth = toolkit.getScreenSize().width;
int screenheight = toolkit.getScreenSize().height;
int x = (screenwidth/2) - (this.getSize().width/2);
int y = (screenheight/2) - (this.getSize().height/2);
setLocation(x, y);


}

/**
* @param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new MainClass().setVisible(true);
}
});
}

// Variables declaration - do not modify
private javax.swing.JTextField address;
private javax.swing.JTextField address1;
private javax.swing.JComboBox cbobook;
private javax.swing.JComboBox cbobook1;
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JButton jButton3;
private javax.swing.JButton jButton4;
private javax.swing.JButton jButton5;
private javax.swing.JButton jButton6;
private javax.swing.JButton jButton7;
private javax.swing.JButton jButton8;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel10;
private javax.swing.JLabel jLabel11;
private javax.swing.JLabel jLabel12;
private javax.swing.JLabel jLabel13;
private javax.swing.JLabel jLabel14;
private javax.swing.JLabel jLabel15;
private javax.swing.JLabel jLabel16;
private javax.swing.JLabel jLabel17;
private javax.swing.JLabel jLabel18;
private javax.swing.JLabel jLabel19;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel20;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JLabel jLabel5;
private javax.swing.JLabel jLabel6;
private javax.swing.JLabel jLabel7;
private javax.swing.JLabel jLabel8;
private javax.swing.JLabel jLabel9;
private javax.swing.JPanel jPanel1;
private javax.swing.JPanel jPanel2;
private javax.swing.JPanel jPanel3;
private javax.swing.JPanel jPanel5;
private javax.swing.JPanel jPanel6;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTabbedPane jTabbedPane1;
private javax.swing.JTabbedPane jTabbedPane4;
private javax.swing.JTable jTable1;
private javax.swing.JTextField num;
private javax.swing.JTextField txtadd;
private javax.swing.JTextField txtchange;
private javax.swing.JTextField txtchange1;
private javax.swing.JTextField txtcontact;
private javax.swing.JTextField txtcontact1;
private javax.swing.JTextField txtid;
private javax.swing.JTextField txtid1;
private javax.swing.JTextField txtname;
private javax.swing.JTextField txtname1;
private javax.swing.JTextField txtpayment;
private javax.swing.JTextField txtpayment1;
private javax.swing.JTextField txtprice;
private javax.swing.JTextField txtprice1;
private javax.swing.JTextField txtremarks;
private javax.swing.JTextField txtremarks1;
private javax.swing.JTextField txtremove;
// End of variables declaration

}

[mtyoung]

just like your Update method, you need to connect to your database and execute 'select' queue to get data from database, get data from ResultSet and add to combobox