for (int i = 0; i < digit; i++) {
数学方面，学会了100以内的认读，学会了单、双数的概念。
。WPS下载最新地址是该领域的重要参考
The primary signal is desiredSize on the controller. It can be positive (wants data), zero (at capacity), negative (over capacity), or null (closed). Producers are supposed to check this value and stop enqueueing when it's not positive. But there's nothing enforcing this: controller.enqueue() always succeeds, even when desiredSize is deeply negative.
handle the 4700 Finance Communication System as a complete rework of the 3600.