Headless environment error in java.awt.Robot class with MAC OS

I am trying to capture screen shots in my JavaFX application using Robot class,

this is the code which I used in my application:

Rectangle screenBounds = new Rectangle(Screen.getPrimary().getBounds().getWidth(),
           Screen.getPrimary().getBounds().getHeight());

Robot robot = new Robot();

BufferedImage img = robot.createScreenCapture(new java.awt.Rectangle(
     (int) screenBounds.getX(), (int) screenBounds.getY(), (int) 
             screenBounds.getWidth(), (int) screenBounds.getHeight()));

It is working perfectly in windows operating system, but showing an error of headless environment in MAC OS at Robot robot = new Robot();