Chapter 15 Exercise 23, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

15.23 (Auto resize stop sign)
Rewrite Programming Exercise 14.15 so that the stop sign’s
width and height are automatically resized when the window is resized.

import javafx.application.Application;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Polygon;
import javafx.scene.text.Font;
import javafx.scene.text.Text;
import javafx.stage.Stage;

public class Exercise_23 extends Application {

    private static double WIDTH = 400;
    private static double HEIGHT = 400;

    StackPane pane = new StackPane();

    @Override
    public void start(Stage primaryStage) throws Exception {

        Polygon polygon = new Polygon();
        polygon.setFill(Color.RED);
        polygon.setStroke(Color.RED);
        Text text = new Text("STOP");
        text.setFont(Font.font(100));
        text.setFill(Color.WHITE);

        pane.getChildren().addAll(polygon, text);

        ObservableList<Double> points = polygon.getPoints();

        Scene scene = new Scene(pane, WIDTH, HEIGHT);
        primaryStage.setScene(scene);
        update(points);
        pane.widthProperty().addListener(e-> {
            update(points);
            double radius = Math.min(pane.getWidth(), pane.getHeight()) * 0.25;
            text.setFont(Font.font(radius));
        });
        primaryStage.setTitle("STOP");
        primaryStage.show();
    }

    private void update(ObservableList<Double> points) {
        double x = pane.getWidth() / 2;
        double y = pane.getHeight() / 2;
        double radius1 = Math.min(pane.getWidth(), pane.getHeight()) * 0.4;

        points.clear();
        for (int i = 0; i < 8; i++) {
            points.add(x + radius1 * Math.cos(Math.toRadians(i * 45 + 45 / 2)));
            points.add(y - radius1 * Math.sin(Math.toRadians(i * 45 + 45 / 2)));
        }
    }

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