主语+ shall/will have been doing
I shall have been working here in this factory for twenty years by the end of the year. 到今 年年底,我将在这个工厂工作20年了
The play is coming off in August. By then the play will have been running for three months. 这个剧将于8月停演。到那时为止,这个剧将连演三个月了。
By Friday midday, they will have been working on it for seven days.到星期五中午,他们就在这个工程上干了7天了。