Why immutability by default matters in Kotlin - See It in Action

Why immutability by default matters

📖 Scenario: Imagine you are managing a list of favorite fruits in a program. You want to make sure that once you set this list, it cannot be changed accidentally by other parts of your program. This helps keep your data safe and predictable.

🎯 Goal: You will create an immutable list of fruits, then try to change it safely by creating a new list. This shows why immutability by default is important in Kotlin.

📋 What You'll Learn

Create an immutable list of fruits called fruits with values "Apple", "Banana", and "Cherry"

Create a new list called newFruits by adding "Date" to the original list

Print both fruits and newFruits to show the difference

💡 Why This Matters

🌍 Real World

Immutable data helps avoid bugs in apps by preventing accidental changes to important data.

💼 Career

Many Kotlin projects use immutability to write safer, easier-to-maintain code, especially in Android development.

1

Create an immutable list of fruits

Create an immutable list called fruits with the exact values "Apple", "Banana", and "Cherry" using listOf().

Kotlin

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

Need a hint?

Use val and listOf() to create an immutable list.

2

Create a new list by adding a fruit

Create a new list called newFruits by adding "Date" to the fruits list using the plus operator.

Kotlin

val fruits = listOf("Apple", "Banana", "Cherry")
# Create a new list called newFruits by adding "Date" to fruits
# Your code here

Need a hint?

Use val newFruits = fruits + "Date" to create a new list with the added fruit.

3

Print both lists to compare

Print the fruits list and the newFruits list using two separate println statements.

Kotlin

val fruits = listOf("Apple", "Banana", "Cherry")
val newFruits = fruits + "Date"
# Print fruits and newFruits
# Your code here

Need a hint?

Use println() to show the contents of both lists.

4

Observe immutability by default

Run the program to see that the original fruits list stays unchanged, while newFruits has the added fruit. This shows why immutability by default matters.

Kotlin

val fruits = listOf("Apple", "Banana", "Cherry")
val newFruits = fruits + "Date"
println(fruits)
println(newFruits)
# Run the program to see the output

Need a hint?

The original list does not change. The new list has the extra fruit.