student fxml controller

i have a similar code for teacher that populate database to table view and it works but dont know why am having error in this one the last error points to
teacherTable.setItems(ban);

import java.sql.Connection;

import java.sql.DriverManager;


import java.sql.ResultSet;

import com.mysql.jdbc.PreparedStatement;

import java.sql.SQLException;
import java.util.Calendar;

import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.control.DatePicker;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.TextField;


public class StudentZoneController {
 Connection con;
 PreparedStatement p;
 String rowid,fname,lname,age,sex,cl;
 ResultSet set;
 Alert popup;




    @FXML
     private TableView<usera> teacherTable;


    @FXML
    private TableColumn<usera, String> ROWID;

    @FXML
    private TableColumn<usera, String> FIRSTNAME;

    @FXML
    private TableColumn<usera, String> LASTNAME;

    @FXML
    private TableColumn<usera, String> AGE;

    @FXML
    private TableColumn<usera, String> SEX;

    @FXML
    private TableColumn<usera, String> CLASS;



@FXML
private void load ()
{


     ObservableList<usera> ban =FXCollections.observableArrayList( );

    teacherTable.setItems(ban);

}

@FXML
private void initialize()
{
    ROWID.setCellValueFactory(new PropertyValueFactory<usera,String>("rowid"));
    FIRSTNAME.setCellValueFactory(new PropertyValueFactory<usera,String>("firstname"));
    LASTNAME.setCellValueFactory(new PropertyValueFactory<usera,String>("lastname"));
    AGE.setCellValueFactory(new PropertyValueFactory<usera,String>("age"));
    SEX.setCellValueFactory(new PropertyValueFactory<usera,String>("sex"));
    CLASS.setCellValueFactory(new PropertyValueFactory<usera,String>("primary"));

}

@FXML
private TextField t1;

@FXML
private TextField t2;

@FXML
private TextField t3;

@FXML
private DatePicker dob;


@FXML
private TextField t4;

@FXML
private TextField t5;

@FXML
private TextField t6;

@FXML
private TextField t7;

@FXML
private TextField t8;

@FXML
private TextField t9;

@FXML
private TextField t10;

@FXML
private TextField t11;

@FXML
private TextField t12;

@FXML
private TextField t13;










@FXML
private void showAge()
{
   Calendar now = Calendar.getInstance();
   int year = now.get(Calendar.YEAR);
   int birth = (dob.getValue().getYear());
   int age = year-birth;
   t4.setText(Integer.toString(age) + "years old");



}





    @FXML
    private void addNewUser() throws SQLException
    {

        try
        {
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            com.mysql.jdbc.Connection con =(com.mysql.jdbc.Connection) DriverManager.getConnection("jdbc:mysql://localhost/school?"+"user=root&password =");
             p = (com.mysql.jdbc.PreparedStatement)con.prepareStatement("insert into students values(?,?,?,?,?,?)");
             p.setString(1, t1.getText());
             p.setString(2, t2.getText());
             p.setString(3, t3.getText());
             p.setString(4, t4.getText());
             p.setString(5, t5.getText());
             p.setString(6, t6.getText());

             popup = new Alert(AlertType.INFORMATION);
             popup.setTitle("INFORMATION DIALOG");
             popup.setHeaderText(null);
             popup.setContentText("user created");
             popup.showAndWait();

             p.executeUpdate();
             p.close();
             clearFields();
        }

        catch(Exception eb)
        {

        }



    }



    @FXML
    private void deleteStudent()
    {

        try
        {
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            com.mysql.jdbc.Connection con =(com.mysql.jdbc.Connection) DriverManager.getConnection("jdbc:mysql://localhost/school?"+"user=root&password =");
             p = (com.mysql.jdbc.PreparedStatement)con.prepareStatement("delete from students where FIRSTNAME = ? || LASTNAME = ?");
             p.setString(1, t2.getText());
             p.setString(2, t3.getText());

             popup = new Alert(AlertType.INFORMATION);
             popup.setTitle("INFORMATION DIALOG");
             popup.setHeaderText(null);
             popup.setContentText("STUDENT DELETED");
             popup.showAndWait();
             refreshDelete();

             p.executeUpdate();
        }

        catch(Exception l)
        {
             popup = new Alert(AlertType.INFORMATION);
             popup.setTitle("INFORMATION DIALOG");
             popup.setHeaderText(null);
             popup.setContentText(l.getMessage());
             popup.showAndWait();


        }


    }


    private void clearFields()
    {
        t1.setText("");
        t2.setText("");
        t3.setText("");
        t4.setText("");
        t5.setText("");
        t6.setText("");
        dob.setValue(null);



    }

    @FXML
    private void resetFields()
    {
        t9.clear();
        t10.clear();
        t11.clear();
        t12.clear();
        t13.clear();
    }
    private void refreshDelete()
    {

        t2.clear();
        t3.clear();
    }



}