First let me say that I love this book.
The examples in 2.2 include printing the results along with the code to do the various transforms…which IMHO somewhat hides the beauty and simplicity of the new style.
A similar comment applies in 2.3 at collections/fpij/PickElements.java. It could use a touch more clarity on what friends.stream().filter(…) would return vs. what we get when the .collect() clause is added.
These are nits to a wonderful book that is changing my thinking about Scala vs. “new” Java.