Bloch used the function in the course of implementing TimSort, but copied it directly from Sun's version of the Arrays class (it existed long before Bloch worked for Google). And the reason he did that was because he thought TimSort was going to be contributed and added to Arrays, where it would have direct access (and the copying would at that point be removed). That never happened, which lead to this count of infringement.
It's absolutely ridiculous though. Even though they infringed the damages for that infringement should be about $100, which is the maximum amount you'd have to spend to reproduce that in a clean room. Reimplementations of that method would look pretty much byte-code identical so Oracle really has no basis for seeking anything more than trivial damages.