The affirmative future perfect tense consists of:
The subject + will + have + P.P (the past participle form of the verb)
For example:
By 2020, the government will have completed the bridge.
The negative future perfect tense consists of:
The subject + will not (won’t) + have + P.P (the past participle form of the verb)
For example:
By tomorrow, my mother will not have returned home.
The interrogative future perfect tense:
How to make questions using the future perfect tense:
Will + the subject (noun/ pronoun) + have + P.P + the rest of the sentence?
For example:
The question: Will they have finished the competition by next Monday?
The answer: Yes, they will have finished the competition. / No, they will not have finished the competition.
Note: questions made with question words (how, when, where, why, etc,) are constructed as follows:
Question word + will + the subject (noun/ pronoun) + have + P.P + the rest of the sentence?
For example:
The question: When will they have finished the competition?
The answer: They will have finished the competition by next week.
When to use the future perfect tense?
Words that express the future perfect tense:
The future perfect tense is used to make predictions about something that will be completed in a specific time in the future.
In this pattern, it always comes with the next expressions:
1. By this time + (a future timing) such as: tomorrow, next week, next year, etc.
For example:
 By this time next week, I will have finished my book.
2. By + exact time such as: tomorrow, next week, next year, etc.
For example:
– By tomorrow, my friend will have been in Paris.
– We will have decorated our home by next month.
3. In + a period of time such as: 4 years’ time, a week’s time, etc.
For example:
In a week’s time, I will have taken my vacation.