概念：表示某種情況下一直持續(xù)到說話人所提及的時間。將來完成時用來表示在將來某一時間以前已經(jīng)完成或一直持續(xù)的動作。經(jīng)常與before+將來時間或by+將來時間連用，也可與before或by the time引導的現(xiàn)在時的從句連用。
結構：shall/will + have +過去分詞。 例如：

Before long he will have forgotten all about the matter.

不久他就會全然忘記這件事的。

I shall have been working here in this factory for twenty years by the end of the year.

到今年年底，我將在這個工廠工作20年了

If we don't hurry up the store will have been closing before we get there.

咱們如不快一點兒，等我們到了那兒，店門就會關了。

The play is coming off in August. By then the play will have been running for three months.

這個劇將于8月停演。到那時為止，這個劇將連演三個月了。

1.表示在將來某一時間之前已完成的動作，并往往對將來某一時間產生影響。
We shall have learned 12 units by the end of this term.

到這個學期末，我們將學完12個單元。

By the time you get home I will have cleaned the house from top to bottom.

你到家之前我將把房子徹底打掃一遍。

2.表示推測，相當于"must have done"結構。
You will have heard of this, I guess.

我想你已經(jīng)聽說過這件事了。

I am sure he will have got the information.

我相信他一定得到了這個信息。