os = createImage(width, height); if (os == null) throw new IllegalArgumentException("createImage failed"); pg = os.getGraphics();
offScreenImage = createImage(width, height);  pg = offScreenImage.getGraphics();
		public void addNotify() {			super.addNotify();			os = createImage(width, height);			if (os == null)				throw new IllegalArgumentException("createImage failed");			pg = os.getGraphics();		}