Select an Item in a JComboBox with Multiple Keystrokes in Java

//from  w ww  .java  2  s . c  o m
import java.awt.BorderLayout;

import javax.swing.ComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Main {
  public static void main(String[] argv) throws Exception {
    String[] items = { "A", "A", "B", "B", "C", "C" };
    JComboBox cb = new JComboBox(items);
    cb.setKeySelectionManager(new MyKeySelectionManager());
    
    JPanel panel = new JPanel();
    panel.setLayout(new BorderLayout(10, 10));

    panel.add(cb, BorderLayout.CENTER);
    JFrame f = new JFrame();
    f.add(panel);
    f.pack();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);
  }
}

class MyKeySelectionManager implements JComboBox.KeySelectionManager {
  long lastKeyTime = 0;
  String pattern = "";

  public int selectionForKey(char aKey, ComboBoxModel model) {
    int selIx = 01;
    Object sel = model.getSelectedItem();
    if (sel != null) {
      for (int i = 0; i < model.getSize(); i++) {
        if (sel.equals(model.getElementAt(i))) {
          selIx = i;
          break;
        }
      }
    }
    long curTime = System.currentTimeMillis();
    if (curTime - lastKeyTime < 300) {
      pattern += ("" + aKey).toLowerCase();
    } else {
      pattern = ("" + aKey).toLowerCase();
    }
    lastKeyTime = curTime;
    for (int i = selIx + 1; i < model.getSize(); i++) {
      String s = model.getElementAt(i).toString().toLowerCase();
      if (s.startsWith(pattern)) {
        return i;
      }
    }
    for (int i = 0; i < selIx; i++) {
      if (model.getElementAt(i) != null) {
        String s = model.getElementAt(i).toString().toLowerCase();
        if (s.startsWith(pattern)) {
          return i;
        }
      }
    }
    return -1;
  }
}