Chapter 15 Exercise 18, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

15.18 (Move a rectangle using mouse)
Write a program that displays a rectangle.
You can point the mouse inside the rectangle and drag
(i.e., move with mouse pressed) the rectangle wherever the mouse goes.
The mouse point becomes the center of the rectangle.

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;

public class Exercise_18 extends Application {

    @Override
    public void start(Stage primaryStage) {

        double width = 500;
        double height = 500;

        Rectangle rec = new Rectangle(width / 2.5, height / 2.5, 100, 75);
        rec.setFill(Color.TRANSPARENT);
        rec.setStroke(Color.BLACK);

        Pane pane = new Pane(rec);
        rec.setOnMouseDragged(e-> {
            rec.setX(e.getX() - rec.getWidth() / 2);
            rec.setY(e.getY() - rec.getHeight() / 2);
        });
        primaryStage.setScene(new Scene(pane, width, height));
        primaryStage.setTitle("Move a rectangle using mouse");
        primaryStage.show();
    }

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