Kotlin quiz

Test your Kotlin knowledge with a free interactive quiz — 50 questions with answers and explanations. No signup needed to play.

Why must Kotlin classes be marked `open` to allow inheritance?

1. Why must Kotlin classes be marked `open` to allow inheritance?
2. What is an `init` block?
3. What does `val ages = users.map { it.age }` produce?
4. What does the safe-call operator `?.` do?
5. What is the difference between `List` and `MutableList`?
6. What is an extension function?
7. Which loop iterates over a range of integers `1..10`?
8. What does `object MyService { … }` declare?
9. What is the difference between `==` and `===` in Kotlin?
10. Are `String` template expressions evaluated at compile time?
11. Why does this fail to compile: `var name: String = null`?
12. Which auto-generated members does `data class` provide?

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