Kotlin program: Convert list of strings to uppercase with lambda

Last update on August 27 2025 12:42:46 (UTC/GMT +8 hours)

Write a Kotlin program that implements a lambda expression to convert a list of strings to uppercase.

Pre-Knowledge (Before You Start!)

Before solving this exercise, you should be familiar with the following concepts:

Lambda Expressions: A lambda expression is an anonymous function that allows concise operations on collections.
String Manipulation: The uppercase() function converts a string to uppercase.
Mapping Collections: The map() function transforms each element in a collection based on a given lambda expression.
Iteration: The forEach function is used to iterate through a list and perform an operation on each element.

Hints (Try Before Looking at the Solution!)

Here are some hints to help you solve the problem:

Hint 1: Create a list of lowercase strings.
Hint 2: Use the map() function to apply a transformation to each string.
Hint 3: Inside the lambda expression, use the uppercase() function to convert each string to uppercase.
Hint 4: Store the transformed list in a variable.
Hint 5: Use forEach to iterate over the transformed list and print each string on a new line.

Sample Solution:

Kotlin Code:

fun main() {
    val strings = listOf("red", "green", "blue", "white", "orange", "black")

    val uppercaseList = strings.map { it.uppercase() }

    println("Uppercase List:")
    uppercaseList.forEach { println(it) }
}

Sample Output:

Uppercase List:
RED
GREEN
BLUE
WHITE
ORANGE
BLACK

Explanation:

In the above exercise -

We have a list of strings called "strings". We use the map function on the "strings" list and provide a lambda expression { it.toUpperCase() } as the mapping operation.
Inside the lambda expression, we call the toUpperCase function on each string (it) to convert it to uppercase.
The "map()" function applies the lambda expression to each element of the "strings" list and returns a new list with transformed uppercase strings.
Finally, we print the uppercase list using println and forEach to iterate over each string in the uppercase list. We print it on a separate line.

Go to:

PREV : Sort integer list in descending order with lambda.
NEXT : Check palindrome string.

Kotlin Editor:

Improve this sample solution and post your code through Disqus