Kotlin quiz

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

What is an extension function?

1. What is an extension function?
2. What does the `lazy` delegate do?
3. Which loop iterates over a range of integers `1..10`?
4. How do you implement an interface in Kotlin?
5. What is the difference between `List` and `MutableList`?
6. What does `val ages = users.map { it.age }` produce?
7. What is the `!!` operator?
8. What does this return: `listOf(1, 2, 3).map { it * 2 }`?
9. What is the result type of `if/else` used as an expression?
10. What is the difference between `let` and `apply` scope functions?
11. What is the difference between `==` and `===` in Kotlin?
12. Why does this fail to compile: `var name: String = null`?

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