Blank values for editable JComboBox

Question

Hello,
I have a editable JComboBox that the user can erase its current value and if they simple change focus (like click on a text field on the same panel) the combo box is left blank. i would like to have it so that if the user leaves focus of the box and its blank that current value goes back to what it was before they erased it.
Many thanks,
Jonathan

Answer 1

import java.awt.FlowLayout;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
public class NonBlankCombo {
   JComboBox comboBox;
   Object previousContent;
   void makeUI() {
      Object[] data = {"One", "Two", "Three", "Four", "Five"};
      previousContent = data[0];
      comboBox = new JComboBox(data);
      comboBox.setEditable(true);
      comboBox.addItemListener(new ItemListener() {
         public void itemStateChanged(ItemEvent e) {
            if (e.getStateChange() == ItemEvent.SELECTED
                  && !((String) comboBox.getSelectedItem()).trim().isEmpty()) {
               previousContent = comboBox.getSelectedItem();
      comboBox.getEditor().getEditorComponent().addFocusListener(new FocusListener() {
         public void focusGained(FocusEvent e) {
            previousContent = comboBox.getSelectedItem();
         public void focusLost(FocusEvent e) {
            if (((String)comboBox.getSelectedItem()).trim().isEmpty()) {
               comboBox.setSelectedItem(previousContent);
      JFrame frame = new JFrame("Non-blank Combo");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setSize(200, 100);
      frame.setLayout(new FlowLayout());
      frame.add(comboBox);
      frame.add(new JButton("Click"));
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            new NonBlankCombo().makeUI();
}db