hibernate&hql help

Question

hello, i try to make a gui for some queries i work with netbeans and mysql and i have for example a student table with 6 fields age,id,year,... when i type the query:

from Students

it shows all the fields of the table and all data perfectly

when i type a query like

select year from Students

I got a table but not with the year field only but with some columns and the result write in bytes and not in strings as its defined.

when i want to see it as a gui in netbeans it works fine with the first query "from Students" but when I type the second query with the select clause it show me this error:

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.lang.String cannot be cast to project.entity.Students

when Students is the class wehere all the data fields are defined.

why it gives me this error? it seems that when i use the select clasue or any query that ask not for all the fields it doesn't show the result table as excepted when i try this query from Students where s.Age<30 it works fine and shows all the fields in the table but only with the age <30

here is my code:

    private void executeHQLQuery(String hql) {
    try {
        Session session = HibernateUtil.getSessionFactory().openSession();
        session.beginTransaction();
        Query q = session.createQuery(hql);
        List resultList = q.list();
        displayResult(resultList);
        session.getTransaction().commit();
    } catch (HibernateException he) {
        he.printStackTrace();
    }

}

private void displayResult(List resultList) {
    Vector<String> tableHeaders = new Vector<String>();
    Vector tableData = new Vector();
    tableHeaders.add("StudentID");
    tableHeaders.add("Age");
    tableHeaders.add("City");
    tableHeaders.add("Name");
    tableHeaders.add("SchoolID");
    tableHeaders.add("Year");

    for (Object o : resultList) {
         Students student= (Students) o;
         Vector<Object> oneRow = new Vector<Object>();

       oneRow.add( student.getAge() );
       oneRow.add(student.getStudentId());
       oneRow.add(student.getAge());
       oneRow.add(student.getName());
       oneRow.add(student.getSchoolId());
       oneRow.add(student.getYear());
       tableData.add(oneRow);

    }
    resultTable.setModel(new DefaultTableModel(tableData, tableHeaders));

thanks!!