have finished是什么時態(tài)

　　Once you have finished writing new code.

　　一旦你已經完成了新代碼的編寫工作。

　　I have finished one fourth of my work now.

　　我現在已經完成了我的四分子一的工作。

　　He should have finished the work by now.

　　到現在他應該已經做完那項工作了。