Map transformation in Kotlin - Mini Project: Build & Apply

Map transformation

📖 Scenario: You work in a small bookstore. You have a map of book titles and their prices. You want to update the prices by adding a fixed tax to each book.

🎯 Goal: Build a Kotlin program that creates a map of books and prices, sets a tax rate, applies the tax to each price using map transformation, and prints the updated prices.

📋 What You'll Learn

Create a map called bookPrices with these exact entries: "Kotlin Basics" to 30, "Advanced Kotlin" to 45, "Coroutines Guide" to 40

Create a variable called taxRate and set it to 0.1 (which means 10% tax)

Use mapValues on bookPrices to create a new map called updatedPrices where each price is increased by the tax rate

Print the updatedPrices map

💡 Why This Matters

🌍 Real World

Bookstores and shops often need to update prices by adding taxes or discounts to their product lists.

💼 Career

Understanding map transformations is useful for data processing, pricing algorithms, and working with collections in Kotlin.

1

Create the initial map of book prices

Create a map called bookPrices with these exact entries: "Kotlin Basics" to 30, "Advanced Kotlin" to 45, "Coroutines Guide" to 40

Kotlin

# Create the map bookPrices with the given entries
# Your code here

Need a hint?

Use mapOf to create a map with the given key-value pairs.

2

Set the tax rate

Create a variable called taxRate and set it to 0.1 (which means 10% tax)

Kotlin

val bookPrices = mapOf("Kotlin Basics" to 30, "Advanced Kotlin" to 45, "Coroutines Guide" to 40)
# Create a variable taxRate and set it to 0.1
# Your code here

Need a hint?

Use val taxRate = 0.1 to set the tax rate.

3

Apply the tax to each price using mapValues

Use mapValues on bookPrices to create a new map called updatedPrices where each price is increased by the tax rate

Kotlin

val bookPrices = mapOf("Kotlin Basics" to 30, "Advanced Kotlin" to 45, "Coroutines Guide" to 40)
val taxRate = 0.1
# Create updatedPrices by applying taxRate to each price using mapValues
# Your code here

Need a hint?

Use mapValues with a lambda that multiplies each price by 1 + taxRate and converts to Int.

4

Print the updated prices

Write println(updatedPrices) to display the updated prices map

Kotlin

val bookPrices = mapOf("Kotlin Basics" to 30, "Advanced Kotlin" to 45, "Coroutines Guide" to 40)
val taxRate = 0.1
val updatedPrices = bookPrices.mapValues { (_, price) -> (price * (1 + taxRate)).toInt() }
# Print the updatedPrices map
# Your code here

Need a hint?

Use println(updatedPrices) to show the final map with updated prices.