Combo Box Filter - document lisenter

import java.util.ArrayList;
import java.util.List;

import javax.swing.DefaultComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

public class FilterComboBox extends JComboBox {
    private List<String> array;
    JTextField textfield;

    public FilterComboBox(List<String> array) {
        super(array.toArray());
        this.array = array;
        this.setEditable(true);
        textfield = (JTextField) this.getEditor().getEditorComponent();
//      textfield.addKeyListener(new KeyAdapter() {
//          public void keyReleased(KeyEvent ke) {
//              SwingUtilities.invokeLater(new Runnable() {
//                  public void run() {
//                      comboFilter(textfield.getText());
//                  }
//              });
//          }
//      });
        textfield.getDocument().addDocumentListener(new DocumentListener() {
            @Override
            public void removeUpdate(DocumentEvent e) {
                callFIlter();
            }
            @Override
            public void insertUpdate(DocumentEvent e) {
                callFIlter();
            }
            @Override
            public void changedUpdate(DocumentEvent e) {
            }
        });

    }

    public void callFIlter() {
        try {
            String text = textfield.getDocument().getText(0, textfield.getDocument().getLength());
            comboFilter(text);
        } catch (Exception e2) {
            e2.printStackTrace();
        }
    }

    public synchronized void comboFilter(String enteredText) {
        List<String> autoCompleteArray = new ArrayList<String>();
        for (int i = 0; i < array.size(); i++) {
            if (array.get(i).toLowerCase().contains(enteredText.toLowerCase())) {
                autoCompleteArray.add(array.get(i));
            }
        }
        if (autoCompleteArray.size() > 0) {
            this.setModel(new DefaultComboBoxModel(autoCompleteArray.toArray()));
            this.setSelectedItem(enteredText);
            this.showPopup();
        } else {
            this.hidePopup();
        }
    }

    /* Testing Codes */
    public static List<String> populateArray() {
        List<String> test = new ArrayList<String>();
        test.add("");
        test.add("Mountain Flight");
        test.add("Mount Climbing");
        test.add("Trekking");
        test.add("Rafting");
        test.add("Jungle Safari");
        test.add("Bungie Jumping");
        test.add("Para Gliding");
        return test;
    }
    public static void makeUI() {
        JFrame frame = new JFrame("Adventure in Nepal - Combo Test");

        frame.getContentPane().add(new FilterComboBox(populateArray()));
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

    public static void main(String[] args) throws Exception {
         UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        makeUI();

    }
}