(Draw lines using the arrow keys) Write a program that draws line segments using the arrow keys

/*********************************************************************************
* (Draw lines using the arrow keys) Write a program that draws line segments     *
* using the arrow keys. The line starts from the center of the pane and draws    *
* toward east, north, west, or south when the right-arrow key, up-arrow key,     *
* leftarrow key, or down-arrow key is pressed, as shown in Figure 15.26b.        *
*********************************************************************************/
import javafx.application.Application;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.shape.Polyline;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class Exercise_15_09 extends Application {
	@Override // Override the start method in the Application class
	public void start(Stage primaryStage) {
		// Create a pane 
		Pane pane = new Pane();

		// Create a polyline
		Polyline polyline = new Polyline(new Double(100.0), new Double(100.0));
		polyline.setFill(Color.WHITE);
		polyline.setStroke(Color.BLACK);
		pane.getChildren().add(polyline);
		ObservableList<Double> list = polyline.getPoints();

		// Create and register handler
		pane.setOnKeyPressed(e -> {
			double x = 0, y = 0;
			double length = 10;
			switch (e.getCode()) {
				case DOWN: x = list.get(list.size() - 2);
							  y = list.get(list.size() - 1) + length; break;
				case UP: x = list.get(list.size() - 2);
							y = list.get(list.size() - 1) - length; break;
				case RIGHT: x = list.get(list.size() - 2) + length;
							  y = list.get(list.size() - 1); break;
				case LEFT: x = list.get(list.size() - 2) - length;
							  y = list.get(list.size() - 1); break;

			}
			list.add(x);
			list.add(y); 
		});

		// Create a scene and place it in the stage
		Scene scene = new Scene(pane, 200, 200);
		primaryStage.setTitle("Exercise_15_09"); // Set the stage title
		primaryStage.setScene(scene); // Place the scene in the stage
		primaryStage.show(); // Display the stage

		pane.requestFocus(); // Pane is focused to receive key input 
	}
}