tf[i][j].textProperty().addListener((ObservableValue<? extends String> observable, String oldValue, String newValue) -> {
                    if (!newValue.matches("[1-9]*")) {
                        ((StringProperty) observable).set(oldValue);

                    } else if (newValue.matches("[1-9]*")) {
                        if (newValue.length() > 1) {
                            ((StringProperty) observable).set(newValue.substring(newValue.length() - 1));
                        }
                    }
                });