AutoComplete JComboBox

There are ready-made classes of JComboBox that implement an autocomplete feature and I chose to use Orbital Computer because of its ease of use and simplicity of the code. I added an extra feature in this JComboBox wherein if you press the ESC key, it will automatically select and show the first item in the ComboBoxModel.

To use this class, simply call it like this.

That’s it! No need to actually create a variable for this class since you just pass the JComboBox object as the parameter and the class handles the rest adding the autocomplete feature. Pretty simple right? This is a handy class. Get the code below.

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  1. Your code works great… I’ve made a couple changes so that you can change the ComboBoxModel at runtime with and still have the functionallity:

    package net.perroazul.nalib.desktop;

    import java.awt.event.FocusEvent;
    import java.awt.event.FocusListener;
    import java.awt.event.KeyEvent;
    import java.awt.event.KeyListener;
    import java.beans.PropertyChangeEvent;
    import java.beans.PropertyChangeListener;
    import javax.swing.ComboBoxModel;
    import javax.swing.JComboBox;
    import javax.swing.text.AttributeSet;
    import javax.swing.text.BadLocationException;
    import javax.swing.text.JTextComponent;
    import javax.swing.text.PlainDocument;

    * Tomado de
    public class JComboBoxAutoCompletador extends PlainDocument implements FocusListener, KeyListener, PropertyChangeListener {

    private JComboBox comboBox;
    private ComboBoxModel model;
    private JTextComponent editor;
    private boolean hidePopupOnFocusLoss;

    public JComboBoxAutoCompletador() {
    // Bug 5100422 on Java 1.5: Editable JComboBox won’t hide popup when tabbing out
    hidePopupOnFocusLoss = System.getProperty(“java.version”).startsWith(“1.5”);

    public JComboBoxAutoCompletador(JComboBox jcb) {

    public void registraComboBox(JComboBox jcb) {
    this.comboBox = jcb;
    model = comboBox.getModel();
    editor = (JTextComponent) comboBox.getEditor().getEditorComponent();
    // Highlight whole text when focus gets lost
    // Highlight whole text when user hits enter
    // Handle initially selected object
    Object selected = comboBox.getSelectedItem();
    if(selected != null)

    public void desregistraComboBox() {
    if(comboBox != null) {
    comboBox = null;

    public void insertString(int offs, String str, AttributeSet a) throws BadLocationException {
    // construct the resulting string
    String currentText = getText(0, getLength());
    String beforeOffset = currentText.substring(0, offs);
    String afterOffset = currentText.substring(offs, currentText.length());
    String futureText = beforeOffset + str + afterOffset;
    // lookup and select a matching item
    Object item = lookupItem(futureText);
    if (item != null)
    else {
    // keep old item selected if there is no match
    item = comboBox.getSelectedItem();
    // imitate no insert (later on offs will be incremented by str.length(): selection won’t move forward)
    offs = offs – str.length();
    // provide feedback to the user that his input has been received but can not be accepted
    comboBox.getToolkit().beep(); // when available use: UIManager.getLookAndFeel().provideErrorFeedback(comboBox);

    // remove all text and insert the completed string
    super.remove(0, getLength());
    super.insertString(0, item.toString(), a);

    // if the user selects an item via mouse the the whole string will be inserted.
    // highlight the entire text if this happens.
    if (item.toString().equals(str) && offs == 0)
    else {
    highlightCompletedText(offs + str.length());
    // show popup when the user types
    if(comboBox.isShowing() && comboBox.isFocusOwner())

    private void highlightCompletedText(int start) {

    private Object lookupItem(String pattern) {
    Object selectedItem = model.getSelectedItem();
    // only search for a different item if the currently selected does not match
    if (selectedItem != null && startsWithIgnoreCase(selectedItem.toString(), pattern))
    return selectedItem;
    else {
    // iterate over all items
    for (int i = 0, n = model.getSize(); i < n; i++) {
    Object currentItem = model.getElementAt(i);
    // current item starts with the pattern?
    if(startsWithIgnoreCase(currentItem.toString(), pattern))
    return currentItem;
    // no item starts with the pattern => return null
    return null;

    private boolean startsWithIgnoreCase(String str1, String str2) {
    return str1.toUpperCase().startsWith(str2.toUpperCase());

    public void focusGained(FocusEvent e) { }

    public void focusLost(FocusEvent e) {
    // Workaround for Bug 5100422 – Hide Popup on focus loss

    public void keyTyped(KeyEvent e) { }

    public void keyReleased(KeyEvent e) { }

    public void keyPressed(KeyEvent e) {
    if (e.getKeyCode() == KeyEvent.VK_ENTER)
    else if (e.getKeyCode() == KeyEvent.VK_ESCAPE) {

    public void propertyChange(PropertyChangeEvent evt) {


  2. I am really impressed of that code!! Thanks for sharing. I am looking for how to implement a code like this but if the item is not in the list the combobox will add this to the list of item. I have study some examples but cant find that implementation. Kristina

  3. sir, i want to know where is the getLength and getText methods are defined..

    String currentText = getText(0, getLength);

    and why this line is showing error..
    super.insertString(0, item.toString(), a);
    offs = offs – str.length();

    1. @pooja: these are methods inherited from the Document class. also, this class does not give me errors so there is something wrong in your code

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