public void addStudent(ActionEvent actionEvent) throws IOException {
        if (fieldWithName.getText().length()>0 & filedWithID.getText().length()>0 &fieldWithSurname.getText().length()>0) {
            Student addedStudent=new Student(filedWithID.getText(),fieldWithName.getText(),fieldWithSurname.getText());
            FXMLLoader loader = new FXMLLoader(getClass().getResource("sample.fxml"));
            Controller register = loader.getController();
            ObservableList<Student> list=FXCollections.observableArrayList();
            list.add(addedStudent);
            System.out.println(register.tableOfStudents.getColumns().toString()); //tableOfStudents to mój TableView z sample.fxml
        }
        else {

        }

    }