Introduction

In Scala, a List is an immutable sequence of elements. Unlike Arrays, which are mutable, Lists provide a functional approach to handling collections.

Creating a List

A List can be created easily using the List keyword:

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val listOfInt = List(3, 5, 7)

List Concatenation (:::)

To concatenate two lists, use the ::: operator:

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val firstList = List(1, 2, 3)
val secondList = List(3, 5, 7)
val firstSecondCombined = firstList ::: secondList
// Result: List(1, 2, 3, 3, 5, 7)

Prepending Elements (::)

The :: operator is used to prepend a new element to the beginning of an existing list:

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val threeFour = List("three", "four")
val twoThreeFour = "two" :: threeFour
// Result: List("two", "three", "four")

Lists vs Arrays

Key Takeaway

Use Lists when working with immutable collections in a functional style, and Arrays when you need mutable collections with fast indexed access.