17 U.S.C. §107 does include a list of purposes which, while not exhaustive, is intended to show the sort of things which constitute fair use -- things which Android's use of Java code is far removed from.

That isn't too surprising, given that functional compatibility really isn't the kind of thing you would expect a copyright law to discuss. If copyright is being stretched to cover this new realm, then it also needs to be assessed for what should qualify as fair use in this realm.