code: public void registerPainter(Painter painter) {
  		if (painters.containsKey(painter.getPaintableClassName())) {
  			List<Painter> list = painters.remove(painter.getPaintableClassName());
  			list.add(painter);
  			this.painters.put(painter.getPaintableClassName(), list);
  		} else {
  			List<Painter> list = new ArrayList<Painter>();
  			list.add(painter);
  			this.painters.put(painter.getPaintableClassName(), list);
  		}
  	}
docs: Register a new painter to this visitor.
  
  @param painter
  The painter itself.