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 filterIsInstance function fails to remove the non-matching menu items, and both lines of output display all the unfiltered data. Enjoy drinking your pizza!
The angle-bracketed parameter that distinguishes a Set<Food> from a Set<Drink> is obvious to us in the code, but it turns out not to be included in the compiled program. At runtime, all three Set objects have the same type.
Kotlin’s compiler normally prohibits impossible type checks like this, but the filterIsInstance function adds enough indirection to mask the problem.
Generic Type Erasure
Like the array we used in Puzzle 8, What’s in the Box?, Set<Food> is a generic type. It’s made up of a base type, Set, and a type parameter, Food.
When you compile your program, the type ...
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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.
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