将来完成时是用在表示在将来某一时间以前已经完成或一直持续的动作。在英语时态中，“时“指动作发生的时间，”态“指动作的样子和状态。
状态已完成：表示某事持续到将来某一时为止一直有的状态。并在将来完成。
动作完成：表示将来某一时或另一个将来的动作之前，已经完成的动作或已经对动作会产生一定的影响。
1、表示将来某时之前或某动作发生之前已经完成的动作。
例句：
I shall have finished it by next Friday.到下周五我就把完成了。
She will have written it tomorrow at noon.明天中午她就会写好了。
They will have been graduated from the university before he returns from abroad.在他从国外回来之前他们就会大学毕业了。
2、表示一个持续到将来某时或某动作发生之前的动作。
例句：
By next Monday,she will have studied here for three years.到下周一，她在这里学习就要满3年了。
The concert will begin at half past eight.They will have played half an hour when you arrive.音乐会将在8点半开始。你到达时，他们将已经演奏半小时了。
3、表示对现在或将来可能已经完成动作的推测，对过去实况的推测。
He will have arrived by now.他这是可能已经到了。
He is a somebody now.He will have forgotten his old friends.他现在是个要人了，可能把老朋友都忘了。
You'll have heard that China will launch another spaceship.中国将要发射另一艘宇宙飞船，你可能已经听说了。
