javaerror

package university_bd2f;

import java.net.URL;
import java.util.ResourceBundle;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.ComboBox;
import javafx.scene.control.TableView;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableColumn.CellDataFeatures;
import javafx.scene.control.TableView;

/**
 * FXML Controller class
 *
 * @author srjefers
 */
public class Pnl_notasController implements Initializable {

    @FXML
    private TableView<ObservableList<String>> tbv_notas;

    @FXML
    private ComboBox<ObservableList<Integer>> lvw_semestre;
    private ObservableList<ObservableList<Integer>> data;
    final ObservableList lista = FXCollections.observableArrayList();


    @FXML
    void get_notas(ActionEvent event) {
        int datos;
        datos = lvw_semestre.getValue();
    }

    @FXML
    void set_certificado(ActionEvent event) {

    }
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        //llenar combobox de numeros
        lista.addAll(1,2,3,4,5,6,7);//,"8","9","10","11","12"
        lvw_semestre.setItems(lista);

    }

}