October 2025
Intermediate to advanced
100 pages
2h 27m
English
Content preview from Kotlin Brain TeasersBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Discussion
Our mysteryFootprints variable has a type of Yeti? and a value of null, both of which are possible branches in our when block. But instead of selecting one of those two branches, our program takes the first branch. That’s because null is a valid value for every nullable type and satisfies all four branches of the when block. When more than one branch is matched, Kotlin picks the first matching branch and ignores the rest.
Nullable Type Checks
As you saw in Puzzle 1, Something from Nothing?, null represents a missing value—an empty slot where data would normally be stored.
If you’ve programmed in Java, you might be used to treating null as an oddball outlier in your type declarations and runtime type checks. Java’s instanceof keyword—which ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.