Not only do APIs resemble the chapters and headings of a book, they aslo include the contract that the content under those headings have exactly the same behaviour.

Google didn't just copy the "heading" java.lang.Math.max() they also copied the contract that calling this method should always return the bigger of the two arguments. Ergo, the "content" under the heading is the same, or rather the any differance between the content of Oracle's book and Google's book is irrelevant

As any programmer knows, you code against interfaces not implementations. And if you don't realize that declaring those interfaces take both effort and creativity then you probably aren't a very good programmer.