Hi Pete,
I suspect that our marketing department is trying to put the best possible spin on this book by saying that it's a "favorite" among developers who are moving into Android apps or Java web applications. I don't think we have much data to back up that claim, except for some anecdotal evidence from a handful of satisfied customers. However, I stand by the statement that after completing chapters 1-16, you have the Java skills you need to move on to developing web applications or Android apps. I might also recommend reading some of the later chapters to get a solid foundation for working with databases,
JDBC, and threads. But we review those skills in our servlet/JSP book as well as our Android book and show how they apply within the context of those platforms.
As far as I know, the Java skills presented in chapters 1-16 are all supported in Android development, with the exception of modules, which are clearly marked as only being available from Java 9 (which means you can't yet use them in Android development). We try not to clutter our books with notes/study tips/side margin markers, so you won't find any of those, though we clearly identify the Java skills that were introduced in recent versions of Java in both the text and code examples of the book. So, as long as you know that Android does not support some Java 8 features and doesn't support any Java 9 features, I think our book works really well for preparing you for Android development.
Thanks!