HANNIBAL T posted a comment on http://java-swing-tips.blogspot.com

AddComboBoxTest .java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class AddComboBoxTest {
  @SuppressWarnings("unchecked")
  public static JComboBox makeComboBox(String[] items) {
    //public void addComboBox(String[] items, String label, int position) {
    JComboBox comboBox = new JComboBox();
    //comboBox.setBorder(new RoundedCornerBorder());
    //for(int a=0; a<items.length; a++ ) {
    //    comboBox.insertItemAt(items[a], a);
    //}
    comboBox.setModel(new DefaultComboBoxModel(items));
    return comboBox;
  }
  public static JPanel makeTitledPanel(JComponent comboBox, String label) {
    JPanel panel_objetos = new JPanel(new FlowLayout(FlowLayout.LEFT));
    panel_objetos.setOpaque(false);
    panel_objetos.add(new JLabel(label));
    panel_objetos.add(comboBox);
    return panel_objetos;
  }
  public JComponent makeUI() {
    JPanel panel_filas_padre = new JPanel();

    //de esta forma genero los Jcombobox:
    String[] items_1 = new String[] {"A","B","C","D","F","G"};
    JComboBox comboBox1 = makeComboBox(items_1);
    JPanel p1 = makeTitledPanel(comboBox1, "letras");
    panel_filas_padre.add(p1); //, position);
    //addComboBox(items_1, "letras", 0);
    //-------------------------------/
    String[] items_2 = new String[] {"1","2","3","4","5","6"};
    JComboBox comboBox2 = makeComboBox(items_2);
    JPanel p2 = makeTitledPanel(comboBox2, "numeros");
    panel_filas_padre.add(p2); //, position);
    //addComboBox(items_2, "numeros", 1);
    //----------------------------------/

    comboBox1.addActionListener(new ActionListener() {
      public void actionPerformed(java.awt.event.ActionEvent e) {
        JComboBox c = (JComboBox)e.getSource();
        System.out.println("ITEM_1 = " + c.getSelectedItem());
      }
    });
    comboBox2.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        JComboBox c = (JComboBox)e.getSource();
        System.out.println("ITEM_2 = " + c.getSelectedItem());
      }
    });

    JPanel p = new JPanel(new BorderLayout());
    p.add(panel_filas_padre);
    return p;
  }
  public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
      @Override public void run() {
        createAndShowGUI();
      }
    });
  }
  public static void createAndShowGUI() {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new AddComboBoxTest().makeUI());
    f.setSize(320, 240);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
  }
}