Sybex CSG 11 - strange example

[Rade Koncar]

Hi all,
in a callout "Using flatMap()" by Boyarsky, Jeanne. OCP Oracle Certified Professional Java SE 11 Developer Complete Study Guide (p. 712). Wiley. Kindle Edition.

There is a strange example of using flatMap to create int stream... Why would you use a flat map for this example? FlatMap is used to flatten the content of the collection, and here the collection is ready to be streamed as is, right?

I tested with this code, prints the same result:

       var integerList = List.of(1, 2, 3, 4, 5, 6);

       IntStream flatInts = integerList.stream().flatMapToInt(x -> IntStream.of(x));
       IntStream ints = integerList.stream().mapToInt(x -> x);

       flatInts.forEach(System.out::println);
       ints.forEach(System.out::println);

I got used that they explain some strange solutions later in the text, but there is no explanation for this...

Am I missing something?

[Jeanne Boyarsky]

Rade,
Yes, those examples are equivalent. We were trying to highlight the name of the method so used the simplest possible example.

Page 700 had already introduced the flatMap() method and provided a more realistic example. (lists with 0, 1, and 2 elements) being combined.

So page 712 assumes you've already read what flatMap() does and is just showing the names of the methods for primitive streams.

[Rade Koncar]

ok, thanks Jeanne!
btw, I proposed one errata on this thread https://coderanch.com/t/734831/certification/Java-OCP-Developer-Complete-Study (it is the one about numeric literals)

[Jeanne Boyarsky]

I didn't get to that thread yet. But the "Kindle numbering problem" isn't an errata. It is an Amazon rendering thing that we nor our publisher have any control over.