How to add lines in combobox?

Question

I want to add very thick colored lines in this combobox so ..
how do i do that..
thanks
public class NewJFrame extends javax.swing.JFrame {
    /** Creates new form NewJFrame */
    public NewJFrame() {
        initComponents();      
    // <editor-fold defaultstate="collapsed" desc=" Generated Code ">
    private void initComponents() {
        jComboBox1 = new javax.swing.JComboBox();
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        getContentPane().add(jComboBox1, java.awt.BorderLayout.NORTH);
        pack();
    // </editor-fold>
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new NewJFrame().setVisible(true);
    // Variables declaration - do not modify
    private javax.swing.JComboBox jComboBox1;
    // End of variables declaration
}

Answer 1

I am exaplaining the code here.Please check once again.
import java.awt.Component;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.Vector;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JSeparator;
import javax.swing.ListCellRenderer;
import javax.swing.UIManager;
import javax.swing.border.EmptyBorder;
* @version 1.0 12/25/98
public class BlockComboBoxExample extends JFrame {
  final String SEPARATOR = "SEPARATOR";
  public BlockComboBoxExample() {
    super("Block ComboBox Example");
    String[][] str = { { "A", "B", "C" }, { "1", "2", "3" },
        { "abc", "def", "ghi" } };
    JComboBox combo = new JComboBox(makeVectorData(str));
    combo.setRenderer(new ComboBoxRenderer());
    combo.addActionListener(new BlockComboListener(combo));
    getContentPane().setLayout(new FlowLayout());
    getContentPane().add(combo);
    setSize(300, 100);
    setVisible(true);
/*This method makes a vector of data to be added to the combo box by iterating through the String array and after each element of array,the needSeparator is made true indicating a separator must be added*/
private Vector makeVectorData(String[][] str) {
    boolean needSeparator = false;
    Vector data = new Vector();
    for (int i = 0; i < str.length; i++) {
      if (needSeparator) {
        data.addElement(SEPARATOR);
      for (int j = 0; j < str.length; j++) {
data.addElement(str[i][j]);
needSeparator = true;
return data;
public static void main(String args[]) {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
} catch (Exception evt) {}
BlockComboBoxExample frame = new BlockComboBoxExample();
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
/*This class is used to render the elements in ComboBox.When adding elements it checks for Separator,and if it is SEPARATOR then it returns a JSeparator object,causing a separator to be added in combo box.*/
class ComboBoxRenderer extends JLabel implements ListCellRenderer {
JSeparator separator;
public ComboBoxRenderer() {
setOpaque(true);
setBorder(new EmptyBorder(1, 1, 1, 1));
separator = new JSeparator(JSeparator.HORIZONTAL);
public Component getListCellRendererComponent(JList list, Object value,
int index, boolean isSelected, boolean cellHasFocus) {
String str = (value == null) ? "" : value.toString();
if (SEPARATOR.equals(str)) {
return separator;
if (isSelected) {
setBackground(list.getSelectionBackground());
setForeground(list.getSelectionForeground());
} else {
setBackground(list.getBackground());
setForeground(list.getForeground());
setFont(list.getFont());
setText(str);
return this;
class BlockComboListener implements ActionListener {
JComboBox combo;
Object currentItem;
BlockComboListener(JComboBox combo) {
this.combo = combo;
combo.setSelectedIndex(0);
currentItem = combo.getSelectedItem();
public void actionPerformed(ActionEvent e) {
String tempItem = (String) combo.getSelectedItem();
if (SEPARATOR.equals(tempItem)) {
combo.setSelectedItem(currentItem);
} else {
currentItem = tempItem;
Now you can use the same concept to add separator to ur combobox.