Swing Java Tutorial

import javax.swing.JComboBox;
import javax.swing.event.PopupMenuEvent;
import javax.swing.event.PopupMenuListener;
public class Main {
  public static void main(String[] argv) throws Exception {
    String[] items = { "item1", "item2" };
    JComboBox cb = new JComboBox(items);
    cb.setEditable(true);
    MyPopupMenuListener actionListener = new MyPopupMenuListener();
    cb.addPopupMenuListener(actionListener);
  }
}
class MyPopupMenuListener implements PopupMenuListener {
  public void popupMenuWillBecomeVisible(PopupMenuEvent evt) {
    JComboBox cb = (JComboBox) evt.getSource();
  }
  public void popupMenuWillBecomeInvisible(PopupMenuEvent evt) {
    JComboBox cb = (JComboBox) evt.getSource();
  }
  public void popupMenuCanceled(PopupMenuEvent evt) {
    JComboBox cb = (JComboBox) evt.getSource();
  }
}