一、將來完成時：
1.構成：shall / will have + 過去分詞
2.功能：表示將來某時之前已經完成的動作。
→They will have been here for 5 years next Friday.
→By the end of next term, the students will have finished the book.
二、過去將來完成時：
1.構成：would / should have + 過去分詞
2.功能：表示從過去某個時間看將來某時之前已經完成的動作。
→He said that they would have arrived by seven o'clock.
三、將來完成進行時：
1.構成：shall / will have been + 現在分詞
2.功能：表示某一動作將繼續到將來某時，且該動作此時尚未發生。
→We shall have been staying here for four weeks when Tom arrives.
→It will have been raining for a week if it does not stop tomorrow.
將來完成時特點：
·表示將來完成：即表示到將來某個時間為止勢必會完成或預計要完成的動作。
Maybe by then you will have changed your mind.
也許到時候你已經改變主意了。
I hope I'll have finished the work by the end of the month.
我希望我這個月底能完成工作。
·表示動詞的持續：即表示某種狀況將一直持續到說話人所提及某一將來時間。
We will have been married a year on June 25th.
到6月25日我們倆結婚就滿1年了。
By this time next week, I will have worked for this company for 24 years. 到下星期此刻，我已經為該公司幹了24年了。
·表示推測：即表示根據某情況作出的推測
There will have been a definite result before Friday.
星期五以前將肯定會有結果。