How to make jcombobox display all by itlself?

Question

Hello all -
Is there a way to make a jcombobox object display its column of items implicitly?
For example, suppose a program has a combobox filled up with names. And, suppose the first item says "toggle sort", which affects how the items are sorted in the combobox (eg, pressing it should cause the list to sort the displayed names based on first name, another press bases the sort on the last name...). The behavior I am aiming for is that when the user presses the "toggle sort" item, the combobox displays its items again awaiting further selection from the user (but not the first item). Know how to fire such an event?
private void namesComboBoxActionPerformed(ActionEvent evt) {
   int selected = namesComboBox.getSelectedIndex();
   if (selected == 0) {
      // some code should result in the namesComboBox displaying its items again. What is it please?
}

Answer 1

Here is a simple code, I don't know if its the correct way to do this sort of thing but it works:
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Collections;
import javax.swing.*;
* Sorting Combobox....
* @author talha
public class ComboSort extends JFrame{
    ArrayList<ComboData> data;
    JComboBox combo;
    public ComboSort() {
        super("Combo Sorting");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        populateData();
        Collections.sort(data);
        // I don't know how much of the combobox model should be overridden!
        combo=new JComboBox(new DefaultComboBoxModel() {
            @Override
            public Object getElementAt(int index) {
                return (index==0)?"Toggle Sort":data.get(index-1);
            @Override
            public int getSize() {
                return data.size()+1;
            @Override
            public int getIndexOf(Object anObject) {
                return (anObject instanceof String)?0:data.indexOf(anObject)+1;
        combo.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if(combo.getSelectedIndex()==0){
                    ComboData.toggleSort();
                    Collections.sort(data);
                    //edited to make the pop up visible....
                    SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                            combo.setPopupVisible(true);
        combo.setRenderer(new DefaultListCellRenderer() {
            @Override
            public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
                Component renderer=super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
                if(value instanceof String){
                    renderer.setForeground(Color.BLUE);
                    renderer.setBackground(Color.YELLOW);
                return renderer;
        // you can remove following....
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                combo.setSelectedIndex(0);
        getContentPane().setLayout(new FlowLayout());
        getContentPane().add(new JLabel("Heads of State:"));
        getContentPane().add(combo);
        setSize(300, 300);
        setLocationRelativeTo(null);
    private void populateData() {
        data=new ArrayList<ComboData>();
        data.add(new ComboData("Barak", "Obama"));
        data.add(new ComboData("Gordon", "Brown"));
        data.add(new ComboData("Nicolas", "Sarkozy"));
        data.add(new ComboData("Angela", "Merkel"));
        data.add(new ComboData("Wen", "Jiabao"));
        data.add(new ComboData("Taro", "Aso"));
        data.add(new ComboData("Manmohan", "Singh"));
        data.add(new ComboData("Asif", "Zardari"));
        data.add(new ComboData("Mahmoud", "Ahmedinejad"));
        data.add(new ComboData("Hugo", "Chavez"));
        data.add(new ComboData("Raul", "Castro"));
    public static void main(String args[]){
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new ComboSort().setVisible(true);
class ComboData implements Comparable{
    String firstname;
    String lastname;
    static boolean sortFirstName;
    public ComboData(String firstname, String lastname) {
        this.firstname = firstname;
        this.lastname = lastname;
    @Override
    public String toString() {
        return firstname+" "+lastname;
    public static void toggleSort(){
        sortFirstName=!sortFirstName;
    public int compareTo(Object o) {
        ComboData other=(ComboData)o;
        if(sortFirstName)return firstname.compareTo(other.firstname);
        else return lastname.compareTo(other.lastname);
}Thanks!
Edit: Reread your original post and made few editions... but I still don't think that this is what you need (but now its much better) :-)
Edited by: T.B.M on Apr 19, 2009 1:16 PM