今、私は実行時エラーを受け取ります。'java.lang.UnsupportedOperationException:まだ実装されていません'どうすれば復元できますか。
 private void btnlogActionPerformed(java.awt.event.ActionEvent evt) {
    user=txtuser.getText();
    char[] pass=jPasswordField1.getPassword();
    String passString=new String(pass);
    try{
      Connection con = createConnection();
      String sql = "INSERT INTO login(username,Password) VALUES ('" + user + "','" + passString + "')";
      Statement st = con.prepareStatement(sql);
      st.executeUpdate(sql);
    }
    catch(Exception e){
      JOptionPane.showMessageDialog(null,"Exception: "+ e.toString());
    }
  }
  public static void main(String args[]) {
    try {
      Class.forName("com.mysql.jdbc.Driver");
      String connectionUrl = "jdbc:mysql://localhost/Stock?"+
        "user=root&password=";
      Connection con = DriverManager.getConnection(connectionUrl);
    } catch (SQLException e) {
      JOptionPane.showMessageDialog(null,"SQL Exception: "+ e.toString());
    } catch (ClassNotFoundException cE) {
      JOptionPane.showMessageDialog(null,"Class Not Found Exception: "+ cE.toString());
    }
  }