如何只接受小写字母和数字，并将它们放在单独的TextFields中？

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;

import java.util.regex.Pattern;

public class Main extends Application {

    private static final Pattern VALID_PATTERN = Pattern.compile("[a-z0-9]*");

    @Override
    public void start(Stage primaryStage) {
        GridPane gridPane = new GridPane();
        gridPane.setPadding(new Insets(10));
        gridPane.setHgap(10);

        TextField lowercaseTextField = new TextField();
        TextField digitTextField = new TextField();

        lowercaseTextField.setPromptText("Only lowercase letters");
        digitTextField.setPromptText("Only digits");

        lowercaseTextField.textProperty().addListener((observable, oldValue, newValue) -> {
            if (!isValidInput(newValue)) {
                lowercaseTextField.setText(oldValue);
            }
        });

        digitTextField.textProperty().addListener((observable, oldValue, newValue) -> {
            if (!isValidInput(newValue)) {
                digitTextField.setText(oldValue);
            }
        });

        gridPane.add(lowercaseTextField, 0, 0);
        gridPane.add(digitTextField, 0, 1);

        Scene scene = new Scene(gridPane, 200, 100);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    private boolean isValidInput(String input) {
        return VALID_PATTERN.matcher(input).matches();
    }

    public static void main(String[] args) {
        launch(args);
    }
}