private ConnectionBDD() {
        try
        {
            Class.forName("com.mysql.jdbc.Driver");
            conn= (Connection) DriverManager.getConnection(url,login,passwd); 
            st= (Statement) conn.createStatement(); 
        }
        catch(ClassNotFoundException cnfe){
            Logger.getLogger(ConnectionBDD.class.getName()).log(Level.SEVERE, null, cnfe);
            JOptionPane.showMessageDialog(null,
                "L'application n'a pas pu trouver le driver jdbc",
                "erreur",
                JOptionPane.WARNING_MESSAGE);
        }
        catch(SQLException ex)
        {
            Logger.getLogger(ConnectionBDD.class.getName()).log(Level.SEVERE, null, ex);
            JOptionPane.showMessageDialog(null,
                "L'application n'a pas pu se connecter a la BDD",
                "erreur",
                JOptionPane.WARNING_MESSAGE);
        }
    }