code: private PointBag getPointBag() {
  		PointBag pb = nextFreePointBag;
  		if (pb != null) {
  			nextFreePointBag = pb.next;
  			pb.next = null;
  			return pb;
  		}
  		return new PointBag();
  	}
docs: Create a new point bag (or recycle an old one)
  
  @return The new point bag