Jcombobox don't refresh the element

Question

When i press on change button, the combo box don't shows the new elements, why?
how i can correct this problem without use the combobox.addItem() method for each element in the arraylist?
package combobox;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class UpdateElement extends JPanel implements ActionListener {
     private static final long serialVersionUID = 1L;
     private ArrayList customerBeanList = null;
     private JComboBox jcb = null;
     public UpdateElement() {
          JFrame f = new JFrame("Test");
          f.getContentPane().setLayout(new FlowLayout());
          f.addWindowListener(new WindowAdapter() {
               public void windowClosing(WindowEvent e) {
                    System.exit(0);
          customerBeanList = getCustomerBeanListFirst();
          jcb = new JComboBox(customerBeanList.toArray());
          f.getContentPane().add(jcb);
          f.getContentPane().add(createButtonPanel());
          f.pack();
          f.setSize(300, 120);
          f.setVisible(true);
     private ArrayList getCustomerBeanListFirst() {
          customerBeanList = new ArrayList(3);
          customerBeanList.add(new CustomerBean(1, "customer3", "xxx"));
          customerBeanList.add(new CustomerBean(2, "customer2", "yyy"));
          customerBeanList.add(new CustomerBean(3, "customer3", "zzz"));
          return customerBeanList;
     private ArrayList getCustomerBeanListSecond() {
          customerBeanList = new ArrayList(4);
          customerBeanList.add(new CustomerBean(23, "customer9", "aaa"));
          customerBeanList.add(new CustomerBean(36, "customer10", "bbb"));
          customerBeanList.add(new CustomerBean(67, "customer11", "ccc"));
          customerBeanList.add(new CustomerBean(41, "customer12", "dd"));
          return customerBeanList;
     public static void main(String s[]) {
          new UpdateElement();
     private JPanel createButtonPanel() {
          JButton changeJB = new JButton("Change");
          changeJB.addActionListener(this);
          JPanel panel = new JPanel();
          panel.setLayout(new FlowLayout(FlowLayout.CENTER, 0, 0));
          panel.add(changeJB);
          return panel;
     public void actionPerformed(ActionEvent e) {
          customerBeanList = getCustomerBeanListSecond();
          jcb = new JComboBox(customerBeanList.toArray());
}

Answer 1

jcb = new JComboBox(customerBeanList.toArray());This creates a new combobox, but you didn't add it to the GUI.
The easiest way is to create a new model and then reset the model of the existing combobox:
ComboBoxModel model = new DefaultComboBoxModel( customerBeanList.toArray() );
comboBox.setModel( model );