Introduction to Kotlin Collections and Strings

Welcome to this course! Our goal is to strengthen your understanding of Kotlin by revisiting its basics and preparing you for interviews. In this lesson, we will explore collections—specifically, the types of lists in Kotlin, namely mutable and immutable lists, as well as how to work effectively with strings.

Kotlin offers two flavors of lists, each serving different needs:

• Immutable Lists: Lists where the elements cannot be changed after their creation.
• Mutable Lists: Lists where you can change, add, or remove elements freely.

Here's how you can use immutable lists in Kotlin:

fun main() {
    // Creating an Immutable List
    val list = listOf("apple", "banana", "cherry")

    // Accessing elements using indexing
    val firstElement = list[0] // 'apple'
    val lastElement = list[list.size - 1] // 'cherry'

    // Getting the size of the list
    val size = list.size // 3

    // Printing the list
    println(list) // prints [apple, banana, cherry]
}

Immutable lists are perfect for use cases where you don't need to modify the contents of the list after its creation. You can find more information in the Kotlin documentation for Immutable Lists.

If you need to modify your list, mutable lists are the way to go. Mutable lists support all the operations available for immutable lists, with additional methods for modification:

fun main() {
    // Creating a Mutable List
    val mutableList = mutableListOf("apple", "banana", "cherry")

    // Adding elements
    mutableList.add("date") // adds 'date'

    // Removing elements
    mutableList.remove("banana") // removes 'banana'

    // Accessing sublist
    val sublist = mutableList.subList(1, mutableList.size) // ["cherry", "date"]

    // Finding the index of an element
    val index = mutableList.indexOf("cherry") // 1

    // Sorting the list
    val sortedList = mutableList.sorted() // ["apple", "cherry", "date"]

    // Printing the list
    println(mutableList) // prints [apple, cherry, date]
}

Mutable lists provide flexibility by allowing modification of the list elements even after its creation. Explore more about them in the Kotlin documentation for Mutable Lists.