Overview of Scala Collections: Mutable and Immutable Types with Examples

Scala provides a robust collection framework that includes both mutable and immutable collections.

Mutable collections can be updated or expanded, allowing elements to be added, removed, or modified, while immutable collections never change; operations on them return new collections, leaving the original unchanged.

The most commonly used collection types are:

List : an ordered, linear collection that may contain duplicate elements.

Set : an unordered collection that contains no duplicate elements.

Map : a collection of key‑value pairs, where each key maps to a value.

Tuple : a fixed‑size collection that can hold elements of different types.

Option : a container that may hold a value of a given type or be empty.

Iterator : not a container but a way to access elements of a collection sequentially.

Example definitions for each collection type are shown below:

// Define an integer List
val x = List(1,2,3,4)

// Define a Set
val x = Set(1,3,5,7)

// Define a Map
val x = Map("one" -> 1, "two" -> 2, "three" -> 3)

// Create a Tuple with two different types
val x = (10, "Runoob")

// Define an Option
val x: Option[Int] = Some(5)