Calendar in a JComboBox

import java.awt.*;
import java.awt.event.*;
import java.util.Calendar;
import java.text.SimpleDateFormat;

import javax.swing.*;
import javax.swing.event.PopupMenuListener;
import javax.swing.event.PopupMenuEvent;
import javax.swing.plaf.ComboBoxUI;
import javax.swing.plaf.basic.ComboPopup;
import javax.swing.plaf.metal.MetalComboBoxUI;
import javax.swing.border.Border;
import javax.swing.border.EtchedBorder;
import javax.swing.border.EmptyBorder;

import com.sun.java.swing.plaf.motif.MotifComboBoxUI;
import com.sun.java.swing.plaf.windows.WindowsComboBoxUI;


public class DateComboBox extends JComboBox {

    protected SimpleDateFormat dateFormat = new SimpleDateFormat("MMM d, yyyy");
    public void setDateFormat(SimpleDateFormat dateFormat) {
    this.dateFormat = dateFormat;
    }
    public void setSelectedItem(Object item) {
    // Could put extra logic here or in renderer when item is instanceof Date, Calendar, or String
    // Dont keep a list ... just the currently selected item
    removeAllItems(); // hides the popup if visible
    addItem(item);
    super.setSelectedItem(item);
    }

    public void updateUI() {
    ComboBoxUI cui = (ComboBoxUI) UIManager.getUI(this);
    if (cui instanceof MetalComboBoxUI) {
        cui = new MetalDateComboBoxUI();
    } else if (cui instanceof MotifComboBoxUI) {
        cui = new MotifDateComboBoxUI();
    } else if (cui instanceof WindowsComboBoxUI) {
        cui = new WindowsDateComboBoxUI();
    }
        setUI(cui);
    }

    // Inner classes are used purely to keep DateComboBox component in one file
    //////////////////////////////////////////////////////////////
    // UI Inner classes -- one for each supported Look and Feel
    //////////////////////////////////////////////////////////////

    class MetalDateComboBoxUI extends MetalComboBoxUI {
    protected ComboPopup createPopup() {
        return new DatePopup( comboBox );
    }
    }

    class WindowsDateComboBoxUI extends WindowsComboBoxUI {
    protected ComboPopup createPopup() {
        return new DatePopup( comboBox );
    }
    }

    class MotifDateComboBoxUI extends MotifComboBoxUI {
    protected ComboPopup createPopup() {
        return new DatePopup( comboBox );
    }
    }

    //////////////////////////////////////////////////////////////
    // DatePopup inner class
    //////////////////////////////////////////////////////////////

    class DatePopup implements ComboPopup, MouseMotionListener,
                   MouseListener, KeyListener, PopupMenuListener {

    protected JComboBox comboBox;
    protected Calendar calendar;
    protected JPopupMenu popup;
    protected JLabel monthLabel;
    protected JPanel days = null;
    protected SimpleDateFormat monthFormat = new SimpleDateFormat("MMM yyyy");

    protected Color selectedBackground;
    protected Color selectedForeground;
    protected Color background;
    protected Color foreground;

    public DatePopup(JComboBox comboBox) {
        this.comboBox = comboBox;
        calendar = Calendar.getInstance();
        //String[] dts = {dt};
        int yr  = calendar.get(Calendar.YEAR);
        int mn  = calendar.get(Calendar.MONTH);
        int dts  = calendar.get(Calendar.DATE);
        String dt = dts+"/"+mn+"/"+yr;
        comboBox.addItem(dt);
        // check Look and Feel
        background = UIManager.getColor("ComboBox.background");
        foreground = UIManager.getColor("ComboBox.foreground");
        selectedBackground = UIManager.getColor("ComboBox.selectionBackground");
        selectedForeground = UIManager.getColor("ComboBox.selectionForeground");

        initializePopup();
    }

    //========================================
    // begin ComboPopup method implementations
    //
        public void show() {
        try {
        // if setSelectedItem() was called with a valid date, adjust the calendar
        calendar.setTime( dateFormat.parse( comboBox.getSelectedItem().toString() ) );
        } catch (Exception e) {}
        updatePopup();
        popup.show(comboBox, 0, comboBox.getHeight());
        }

    public void hide() {
        popup.setVisible(false);
    }

    protected JList list = new JList();
    public JList getList() {
        return list;
    }

    public MouseListener getMouseListener() {
        return this;
    }

    public MouseMotionListener getMouseMotionListener() {
        return this;
    }

    public KeyListener getKeyListener() {
        return this;
    }

    public boolean isVisible() {
        return popup.isVisible();
    }

    public void uninstallingUI() {
        popup.removePopupMenuListener(this);
    }


    public void mousePressed( MouseEvent e ) {}
        public void mouseReleased( MouseEvent e ) {}
    // something else registered for MousePressed
    public void mouseClicked(MouseEvent e) {
            if ( !SwingUtilities.isLeftMouseButton(e) )
                return;
            if ( !comboBox.isEnabled() )
                return;
        if ( comboBox.isEditable() ) {
        comboBox.getEditor().getEditorComponent().requestFocus();
        } else {
        comboBox.requestFocus();
        }
        togglePopup();
    }

    protected boolean mouseInside = false;
    public void mouseEntered(MouseEvent e) {
        mouseInside = true;
    }
    public void mouseExited(MouseEvent e) {
        mouseInside = false;
    }

    // MouseMotionListener
    public void mouseDragged(MouseEvent e) {}
    public void mouseMoved(MouseEvent e) {}

    // KeyListener
    public void keyPressed(KeyEvent e) {}
    public void keyTyped(KeyEvent e) {}
    public void keyReleased( KeyEvent e ) {
        if ( e.getKeyCode() == KeyEvent.VK_SPACE ||
         e.getKeyCode() == KeyEvent.VK_ENTER ) {
        togglePopup();
        }
    }

    /**
     * Variables hideNext and mouseInside are used to
     * hide the popupMenu by clicking the mouse in the JComboBox
     */
    public void popupMenuCanceled(PopupMenuEvent e) {}
    protected boolean hideNext = false;
    public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
        hideNext = mouseInside;
    }
    public void popupMenuWillBecomeVisible(PopupMenuEvent e) {}


    protected void togglePopup() {
        if ( isVisible() || hideNext ) {
        hide();
        } else {
        show();
        }
        hideNext = false;
    }


    // Note *** did not use JButton because Popup closes when pressed
    protected JLabel createUpdateButton(final int field, final int amount) {
        final JLabel label = new JLabel();
        final Border selectedBorder = new EtchedBorder();
        final Border unselectedBorder = new EmptyBorder(selectedBorder.getBorderInsets(new JLabel()));
        label.setBorder(unselectedBorder);
        label.setForeground(foreground);
        label.addMouseListener(new MouseAdapter() {
            public void mouseReleased(MouseEvent e) {
            calendar.add(field, amount);
            updatePopup();
            }
            public void mouseEntered(MouseEvent e) {
            label.setBorder(selectedBorder);
            }
            public void mouseExited(MouseEvent e) {
            label.setBorder(unselectedBorder);
            }
        });
        return label;
    }


    protected void initializePopup() {
        JPanel header = new JPanel(); // used Box, but it wasn't Opaque
        header.setLayout(new BoxLayout(header, BoxLayout.X_AXIS));
        header.setBackground(background);
        header.setOpaque(true);

        JLabel label;
        label = createUpdateButton(Calendar.YEAR, -1);
        label.setText("<<");
        label.setToolTipText("Previous Year");

        header.add(Box.createHorizontalStrut(12));
        header.add(label);
        header.add(Box.createHorizontalStrut(12));

        label = createUpdateButton(Calendar.MONTH, -1);
        label.setText("<");
        label.setToolTipText("Previous Month");
        header.add(label);

        monthLabel = new JLabel("", JLabel.CENTER);
        monthLabel.setForeground(foreground);
        header.add(Box.createHorizontalGlue());
        header.add(monthLabel);
        header.add(Box.createHorizontalGlue());

        label = createUpdateButton(Calendar.MONTH, 1);
        label.setText(">");
        label.setToolTipText("Next Month");
        header.add(label);

        label = createUpdateButton(Calendar.YEAR, 1);
        label.setText(">>");
        label.setToolTipText("Next Year");

        header.add(Box.createHorizontalStrut(12));
        header.add(label);
        header.add(Box.createHorizontalStrut(12));

        popup = new JPopupMenu();
        popup.setBorder(BorderFactory.createLineBorder(Color.black));
        popup.setLayout(new BorderLayout());
        popup.setBackground(background);
        popup.addPopupMenuListener(this);
        popup.add(BorderLayout.NORTH, header);
    }

    // update the Popup when either the month or the year of the calendar has been changed
    protected void updatePopup() {
        monthLabel.setText( monthFormat.format(calendar.getTime()) );
        if (days != null) {
        popup.remove(days);
        }
        days = new JPanel(new GridLayout(0, 7));
        days.setBackground(background);
        days.setOpaque(true);

        Calendar setupCalendar = (Calendar) calendar.clone();
        setupCalendar.set(Calendar.DAY_OF_WEEK, setupCalendar.getFirstDayOfWeek());
        for (int i = 0; i < 7; i++) {
        int dayInt = setupCalendar.get(Calendar.DAY_OF_WEEK);
        JLabel label = new JLabel();
        label.setHorizontalAlignment(JLabel.CENTER);
        label.setForeground(foreground);
        if (dayInt == Calendar.SUNDAY) {
            label.setText("Sun");
        } else if (dayInt == Calendar.MONDAY) {
            label.setText("Mon");
        } else if (dayInt == Calendar.TUESDAY) {
            label.setText("Tue");
        } else if (dayInt == Calendar.WEDNESDAY) {
            label.setText("Wed");
        } else if (dayInt == Calendar.THURSDAY) {
            label.setText("Thu");
        } else if (dayInt == Calendar.FRIDAY) {
            label.setText("Fri");
        } else if (dayInt == Calendar.SATURDAY){
            label.setText("Sat");
        }
        days.add(label);
        setupCalendar.roll(Calendar.DAY_OF_WEEK, true);
        }

        setupCalendar = (Calendar) calendar.clone();
        setupCalendar.set(Calendar.DAY_OF_MONTH, 1);
        int first = setupCalendar.get(Calendar.DAY_OF_WEEK);
        for (int i = 0; i < (first - 1); i++) {
        days.add(new JLabel(""));
        }
        for (int i = 1; i <= setupCalendar.getActualMaximum(Calendar.DAY_OF_MONTH); i++) {
        final int day = i;
        final JLabel label = new JLabel(String.valueOf(day));
        label.setHorizontalAlignment(JLabel.CENTER);
        label.setForeground(foreground);
        label.addMouseListener(new MouseListener() {
            public void mousePressed(MouseEvent e) {}
            public void mouseClicked(MouseEvent e) {}
            public void mouseReleased(MouseEvent e) {
                label.setOpaque(false);
                label.setBackground(background);
                label.setForeground(foreground);
                calendar.set(Calendar.DAY_OF_MONTH, day);
                comboBox.setSelectedItem(dateFormat.format(calendar.getTime()));
                hide();
                comboBox.requestFocus();
            }
            public void mouseEntered(MouseEvent e) {
                label.setOpaque(true);
                label.setBackground(selectedBackground);
                label.setForeground(selectedForeground);
            }
            public void mouseExited(MouseEvent e) {
                label.setOpaque(false);
                label.setBackground(background);
                label.setForeground(foreground);
            }
            });

        days.add(label);
        }

        popup.add(BorderLayout.CENTER, days);
        popup.pack();
    }
    }

    public static void main(String args[])
    {
        JFrame f = new JFrame();
        Container c = f.getContentPane();
        c.setLayout(new FlowLayout());
        c.add(new JLabel("Date:"));
        DateComboBox dcb = new DateComboBox();
        c.add(dcb);
        f.addWindowListener(new WindowAdapter()
        {
            public void windowClosing(WindowEvent e)
            {
                System.exit(0);
            }
        });
        f.setSize(200, 100);
        f.show();
    }

}