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" };
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();
int curIx = cb.getSelectedIndex();
char ch = evt.getKeyChar();
JComboBox.KeySelectionManager ksm = cb.getKeySelectionManager();
if (ksm != null) {
// Determine if another item has the same prefix
int ix = ksm.selectionForKey(ch, cb.getModel());
boolean noMatch = ix < 0;
boolean uniqueItem = ix == curIx;
// Display menu if no matching items or the if the selection is not unique
if (noMatch || !uniqueItem) {
cb.showPopup();
}
}
}
}