code: private PointBag freePointBag(PointBag pb) {
  		PointBag next = pb.next;
  		pb.clear();
  		pb.next = nextFreePointBag;
  		nextFreePointBag = pb;
  		return next;
  	}
docs: Release a pooled bag
  
  @param pb The bag to release
  @return The next available bag