将来完成进行时

表示在将来某时某个动作已进行多久了。
* By the end of this month he will have been climbing mountains for twenty years。 到了这个月底他登山就满 20年了。
* We shall have been staying here for four weeks when Tom arrives. 等到汤姆到达的时候我们将会在这里停留4周了。
* It will have been raining for a week if it does not stop tomorrow. 明天雨还不停的话，这雨就会连续下了一个星期了。
* 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，这个剧将连续上演三个月了。