将来完成时表示将来某时某动作已完成或某事易发生：
Tom will have had his exam by 18 December. 汤姆12月18号就已经考完试了。
By this summer we'll have been here for five years. 到今年夏天我们在这里就满五年了。
The train will have left when we get to the station. 我们到火车站时火车已经开了。
将来完成进行时表示在将来某时某个动作已经进行多久了：
By the end of the year she'll have been acting for twenty years. 到今年年底她演戏将满二十年。
In another month's time I'll have been studying here for three years. 再过一个月我在这里学习就满三年了。
By this summer he'll have been training horses for ten years. 到今年夏天他干训马工作就满十年了。
