Image i = new ImageIcon(getClass().getResource("robot.jpg")).getImage();

BufferedImage b = display.getGraphicsConfiguration().createCompatibleImage(i.getWidth(null), i.getHeight(null));

Graphics g = b.getGraphics();

g.drawImage(i,0,0,i.getWidth(null),i.getHeight(null),null);

g.dispose();

display.setBackdrop(new TexturePaint(b, new Rectangle(0,0,i.getWidth(null),i.getHeight(null))));

 

 

But Eclipse indicates there are errors:

Exception in thread "main" java.lang.NullPointerException

at groupSize.FlockersWithUI.init(FlockersWithUI.java:118)

at sim.display.Console.<init>(Console.java:981)

at groupSize.FlockersWithUI.main(FlockersWithUI.java:24)

 

 

Line 118 is:

BufferedImage b = display.getGraphicsConfiguration().createCompatibleImage(i.getWidth(null), i.getHeight(null));

 

I think I have put robot.jpg in the bin folder.