How Apple.com set Apple Touch Icon? Apple Touch Icon is a icon used in Safari 8 favourite new page on OS X,or web clip in Home screen on iOS.
https://developer.apple.com/library/ios/documentation/AppleApplications/Reference/SafariWebContent/ConfiguringWebApplications/ConfiguringWebApplications.html
there is two way to set it,one is using rel="shortcut icon",another is using rel="apple-touch-icon" like http://apple.stackexchange.com do.So I can find icon URL http://cdn.sstatic.net/apple/img/apple-touch-icon.png?v=2a2c3caaec7f
However apple.com doesn't use those two method.How can I find apple.com's apple touch icon URL?
Is it not just http://www.apple.com/apple-touch-icon.png?

From the iOS Developer Library article you pointed to above...


  To specify an icon for the entire website (every page on the website), place an icon file in PNG format in the root document folder called apple-touch-icon.png