Kotlin Tutorials

Kotlin Map keys
Syntax & Examples

Syntax of Map.keys

The syntax of Map.keys property is:

abstract val keys: Set<K>

This keys property of Map returns a read-only Set of all keys in this map.


✐ Examples

1 Get keys from map of numbers and characters

In this example,

  • We create a map named map containing pairs of numbers and characters.
  • We then access the keys using the keys property.
  • The keys are printed to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map = mapOf(1 to 'a', 2 to 'b', 3 to 'c')
    val keys = map.keys
    println(keys)
}

Output

[1, 2, 3]

2 Get keys from map of characters and numbers

In this example,

  • We create a map named map containing pairs of characters and numbers.
  • We then access the keys using the keys property.
  • The keys are printed to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map = mapOf('a' to 1, 'b' to 2, 'c' to 3)
    val keys = map.keys
    println(keys)
}

Output

[a, b, c]

3 Get keys from map of strings and numbers

In this example,

  • We create a map named map containing pairs of strings and numbers.
  • We then access the keys using the keys property.
  • The keys are printed to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map = mapOf("apple" to 1, "banana" to 2, "cherry" to 3)
    val keys = map.keys
    println(keys)
}

Output

[apple, banana, cherry]

Summary

In this Kotlin tutorial, we learned about keys property of Map: the syntax and few working examples with output and detailed explanation for each example.