I will write a preface when I have finished the book.和 I will write a preface when I finish the book 的区别,

I will write a preface when I have finished the book.我完成这本书之后,就写序言.I will write a preface when I finish the book.我完成这本书,就写序言.前一句强调完成,语气更重一些,也可以暗示这本书耗时较多....