JCALENDAR INTERNATIONALISÉ

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DateFormatSymbols;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Locale;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;


public class JCalendar
extends JPanel {
        
    private Locale _locale = getDefaultLocale();
    
    private GregorianCalendar _calendar = new GregorianCalendar();
    
    private DateFormatSymbols _dateSymbols = new DateFormatSymbols();
    
    private SimpleDateFormat _formatMY = new SimpleDateFormat("MMMM yyyy");
    
    private int _firstDayOfWeek = _calendar.getFirstDayOfWeek();
    
    private final JLabel _monthYear = new JLabel("", SwingUtilities.CENTER);
         
    private final JLabel[] _daysOfWeek = new JLabel[7];
    
    private final JButton[] _daysNumber = new JButton[42];
    
    private final ActionListener _changeMonth = new ActionListener() {
        public void actionPerformed(final ActionEvent ae) {
            final int nb = "next".equals(ae.getActionCommand()) ? 1: -1;
            _calendar.add(Calendar.MONTH, nb);
        updateMonthYear();
        updateDaysNumber();
        }
    };
    
    public JCalendar() {
        setLayout(new BorderLayout());
        // Month Panel
        final JPanel monthPanel = new JPanel();
        final JButton previous = new JButton("<<");
        previous.addActionListener(_changeMonth);
        final JButton next = new JButton(">>");
        next.addActionListener(_changeMonth);
        next.setActionCommand("next");
        _monthYear.setPreferredSize(new Dimension(120, 20));
        monthPanel.add(previous);
        monthPanel.add(_monthYear);
        monthPanel.add(next);
        add(monthPanel, BorderLayout.NORTH);
        // Day Panel
        final JPanel dayPanel = new JPanel();
        dayPanel.setLayout(new GridLayout(7, 7));
        for (int i = 0; i < 7; ++i)
            dayPanel.add(_daysOfWeek[i] = new JLabel("", SwingUtilities.CENTER));
        for (int i = 0; i < _daysNumber.length; ++i)
            dayPanel.add(_daysNumber[i] = new JButton());
        add(dayPanel, BorderLayout.CENTER);
        // Remplissage des composants
        updateMonthYear();
        updateDaysOfWeek();
        updateDaysNumber();
    }
    
    // Réactualise la locale et réaffiche le contenu des composants
    private void updateLocale(final Locale locale) {
        _locale = locale;
        final Date tmp = _calendar.getTime();
        _calendar = new GregorianCalendar(_locale);
        _calendar.setTime(tmp);
        _firstDayOfWeek = _calendar.getFirstDayOfWeek();
        _dateSymbols = new DateFormatSymbols(_locale);
        _formatMY = new SimpleDateFormat("MMMM yyyy", _locale);
        updateMonthYear();
        updateDaysOfWeek();
        updateDaysNumber();
    }
    
    // Affiche le mois et l'année en cours
    private void updateMonthYear() {
        _monthYear.setText(_formatMY.format(_calendar.getTime()));
    }
    
    // Affiche les jours de la semaine
    private void updateDaysOfWeek() {
        final String[] weekDays = _dateSymbols.getShortWeekdays();
        for (int i = 1; i < weekDays.length; ++i) {
            final int index = (i - 2 + _firstDayOfWeek) % 7 + 1;
            _daysOfWeek[i - 1].setText(weekDays[index]);
        }
    }
    
    // Affiche le numéro des jours
    private void updateDaysNumber() {
        final Date tmp = _calendar.getTime();
        _calendar.set(Calendar.DAY_OF_MONTH, 1);
        final int firstDay = _calendar.get(Calendar.DAY_OF_WEEK);
        final int LocalFirstDay = (firstDay - _firstDayOfWeek + 7) % 7 + 1;
        boolean full = false;
        for (int i = 0; i < _daysNumber.length; ++i) {
            //Détermine si le composant est affiché ou non
            final boolean isNotEmpty = i < LocalFirstDay - 1 || full;
            _daysNumber[i].setVisible(!isNotEmpty);
            // Affichage du jour
            if (!isNotEmpty) {
                final int dayOfMonth = _calendar.get(Calendar.DAY_OF_MONTH);
                _daysNumber[i].setText(String.valueOf(dayOfMonth));
                _calendar.add(Calendar.DAY_OF_MONTH, 1);
                full = 1 == _calendar.get(Calendar.DAY_OF_MONTH);
            }
        }
        _calendar.setTime(tmp);
    }
    
    
    public static void main(final String[] args)
    throws ParseException {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                final JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.getContentPane().add(new JCalendar());
                frame.pack();
                frame.setVisible(true);
            }
        });
    }
}