It is too slower to download the Xcode by iTunes. So the following is the address downloaded offline by the Apple Developer Download Center
Entrance 1:
step：
1、first either the developer center：https://developer.apple.com/download/more/
2、sign in your developer account number ,and open Developer Tools
3、select xcode in the pop-up list, and then click "+",get the download address.
Remask：of course, Here you can download other contents .
Entrance 2:
step 1:
Enter the developer center:https://developer.apple.com
step 2:
Click the support ,next select Development,and then select Xcode
step 3:
when you see the blue word (is downloaded here),enter it.
step 4:
sign in your development account number。
step 5:
select you like it.
