package test;import javax.swing.JFrame;public class test extends javax.swing.JFrame { private javax.swing.JComboBox jComboBox1 = new javax.swing.JComboBox();; public test() { setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); jComboBox1.addPopupMenuListener(new javax.swing.event.PopupMenuListener() { public void popupMenuCanceled(javax.swing.event.PopupMenuEvent evt) { System.out.println("Popup Menu Cancelled"); } public void popupMenuWillBecomeInvisible(javax.swing.event.PopupMenuEvent evt) { System.out.println("Popup Menu Will Become Invisible"); } public void popupMenuWillBecomeVisible(javax.swing.event.PopupMenuEvent evt) { System.out.println("Popup Menu Will Become Visible"); } }); getContentPane().add(jComboBox1, java.awt.BorderLayout.CENTER); pack(); } public static void main(String args[]) { final JFrame frame = new Main(); java.awt.EventQueue.invokeLater(new Runnable() { public void run() { frame.setVisible(true); } }); }}