public static String printArrayListUsers() throws ClassNotFoundException{
    List <User> users = getUsers();
    StringBuilder sb = new StringBuilder();
        sb.append("<table border=\"1\">");
        sb.append("<tr>");
        sb.append("<th><b>Username</b></th>");
        sb.append("<th><b>First Name</b></th>");
        sb.append("<th><b>Last Name</b></th>");
        sb.append("<th><b>Email</b></th>");
        sb.append("</tr>");
            for(User u : users){

                sb.append("<tr>");
                sb.append("<td>" + u.getUserName() + "</td>");
                sb.append("<td>" + u.getFirstName() + "</td>");
                sb.append("<td>" + u.getLastName() + "</td>");
                sb.append("<td>" + u.getEmail() + "</td>");
                sb.append("</tr>");
            }
            sb.append("</table>");
        return sb.toString();
 }