# Kotlin Collections and Operators (Android)

> Kotlin Collections, functional operators (map, filter, reduce), Sequences, higher-order functions, operator overloading

- 20 interview questions
- Mid-Level
- [Interview Questions: Android](https://sharpskill.dev/en/technologies/android/interview-questions.md)

## 1. What is the difference between List and MutableList in Kotlin?

**Answer**

List is a read-only interface that doesn't allow modifying the collection after creation. MutableList extends List and adds modification methods like add(), remove(), clear(). List guarantees structural immutability.

## 2. How do you create an immutable list in Kotlin?

**Answer**

Use listOf() to create an immutable list. This function returns a read-only List<T>. For a mutable list, use mutableListOf() or arrayListOf().

## 3. What is the map() operator used for on a collection?

**Answer**

map() transforms each element of the collection by applying a function, and returns a new list with the transformed elements. For example: listOf(1,2,3).map { it * 2 } returns [2,4,6].

## 17 more questions available

- What is the filter() operator used for?
- What is the difference between map() and flatMap()?

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