import java.awt.event.KeyAdapter; import java.awt.event.KeyEvent; import javax.swing.JComboBox; public class Main { public static void main(String[] argv) throws Exception { String[] items = { "A", "A", "B", "B", "C", "C" }; JComboBox cb = new JComboBox(items); // Create and register the key listener cb.addKeyListener(new MyKeyListener()); } } class MyKeyListener extends KeyAdapter { public void keyPressed(KeyEvent evt) { JComboBox cb = (JComboBox) evt.getSource(); // Get pressed character char ch = evt.getKeyChar(); // If not a printable character, return if (ch != KeyEvent.CHAR_UNDEFINED) { cb.showPopup(); } } }