Why immutable collections are default in Kotlin - See It in Action

Why Immutable Collections Are Default in Kotlin

📖 Scenario: Imagine you are managing a list of favorite fruits in a Kotlin app. You want to keep this list safe from accidental changes by other parts of your program.

🎯 Goal: You will create an immutable list of fruits, then try to add a fruit to it, and finally print the list to see that it has not changed. This will help you understand why Kotlin uses immutable collections by default.

📋 What You'll Learn

Create an immutable list called fruits with these exact items: "Apple", "Banana", "Cherry"

Create a variable called newFruit and set it to "Orange"

Try to add newFruit to fruits using the plus function and save the result in updatedFruits

Print fruits and updatedFruits to show the original list is unchanged and the new list has the added fruit

💡 Why This Matters

🌍 Real World

Immutable collections are used in apps to keep important data safe from accidental changes, like user settings or fixed lists.

💼 Career

Understanding immutability is important for writing reliable Kotlin code and working with modern Android apps or backend services.

1

Create an immutable list of fruits

Create an immutable list called fruits with these exact items: "Apple", "Banana", "Cherry"

Kotlin

// Create an immutable list called fruits with "Apple", "Banana", "Cherry"
// Your code here

Need a hint?

Use listOf to create an immutable list in Kotlin.

2

Create a new fruit variable

Create a variable called newFruit and set it to "Orange"

Kotlin

val fruits = listOf("Apple", "Banana", "Cherry")
// Create a variable newFruit and set it to "Orange"
// Your code here

Need a hint?

Use val to create a read-only variable.

3

Add the new fruit to the list immutably

Use the plus function to add newFruit to fruits and save the result in a new variable called updatedFruits

Kotlin

val fruits = listOf("Apple", "Banana", "Cherry")
val newFruit = "Orange"
// Use plus to add newFruit to fruits and save in updatedFruits
// Your code here

Need a hint?

The plus function or + operator returns a new list without changing the original.

4

Print both lists to see the difference

Print fruits and updatedFruits using println to show the original list is unchanged and the new list has the added fruit

Kotlin

val fruits = listOf("Apple", "Banana", "Cherry")
val newFruit = "Orange"
val updatedFruits = fruits + newFruit
// Print fruits and updatedFruits
// Your code here

Need a hint?

Use println to display the lists.