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
The mystery here is the finally block’s missing output. Where did it go?
No matter the reason, when a try block exits, the corresponding finally block always runs—right? That’s its job, as we learned in Puzzle 14, Just One More Thing.
But it turns out the suspension-point powered sequence builder has a surprising ability to undermine that critical control-flow guarantee. When we interrupt our number sequence early, the generator code inside just stops in its tracks, and the finally block never runs.
Failing to run finally blocks in a real app can cause bugs and hurt performance by leaving resources unclosed and data in an inconsistent state—so this could be a big problem!
Suspending Sequences
A Sequence in Kotlin produces its values ...
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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.