Kotlin Array - map() Function

The Kotlin array map() function is used to create a list containing elements that result from applying a transformation function to each element of the original array. After the transformation, this function returns the created list containing all elements that match the transformation function.

Syntax

Following is the syntax of Kotlin array map() function −

fun <T, R> Array<out T>.map(
    transform: (T) -> R
): List<R>

Parameters

This function accepts a transform function as a parameter, which represent condition that we are applying in each element.

Return value

This function returns a list.

Example 1

The following is a basic example to demonstrate the use map() function −

fun main(args: Array<String>) {
   val numbers = arrayOf(2, 4, 6)
   //squaring of the elements of list
   println("transformed list:  ${numbers.map { it * it }}")
}

Output

Following is the output −

transformed list:  [4, 16, 36]

Example 2

Now, let's create another example. Here, we creating a map pair of name and age. We then use map() function to display the name with age and value −

fun main(args: Array<String>) {
   //declaring the map pair.
   val peopleToAge = mapOf("Aman" to 23, "Vivek" to 24)
   //printing the name with age.
   println(peopleToAge.map { (name, age) -> "$name is $age years old" })
   println(peopleToAge.map { it.value })
}

Output

Following is the output −

[Aman is 23 years old, Vivek is 24 years old]
[23, 24]

Example 3

The below example creates an array and uses map function to transform the array into list containing boolean value −

fun main(args: Array<String>) {
   val array = arrayOf(1, 2, 3, 4, 5)
   val list = array.map({it%2==0})
   
   println("True if array elements satisfy transform function, otherwise, false")
   println("list: $list")
}

Output

Following is the output −

True if array elements satisfy transform function, otherwise, false
list: [false, true, false, true, false]