Kotlin Tutorials

Kotlin Map getOrElse()
Syntax & Examples

Syntax of Map.getOrElse()

The syntax of Map.getOrElse() extension function is:

fun <K, V> Map<K, V>.getOrElse( key: K, defaultValue: () -> V ): V

This getOrElse() extension function of Map returns the value for the given key if the value is present and not null. Otherwise, returns the result of the defaultValue function.


✐ Examples

1 Get value for key 'b'

In this example,

  • We create a map named map1 containing key-value pairs.
  • We use the getOrElse() function on map1 with key 'b' to retrieve its corresponding value.
  • If the key is present, the corresponding value is returned; otherwise, the default value 0 is returned.
  • The value for key 'b' is printed to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map1 = mapOf("a" to 1, "b" to 2, "c" to 3)
    val value1 = map1.getOrElse("b") { 0 }
    println(value1)
}

Output

2

2 Get value for key 2

In this example,

  • We create a map named map2 containing key-value pairs.
  • We use the getOrElse() function on map2 with key 2 to retrieve its corresponding value.
  • If the key is present, the corresponding value is returned; otherwise, the default value 'x' is returned.
  • The value for key 2 is printed to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map2 = mapOf(1 to 'a', 2 to 'b', 3 to 'c')
    val value2 = map2.getOrElse(2) { 'x' }
    println(value2)
}

Output

b

3 Get value for key 4

In this example,

  • We create a map named map3 containing key-value pairs.
  • We use the getOrElse() function on map3 with key 4 to retrieve its corresponding value.
  • If the key is present, the corresponding value is returned; otherwise, the default value 'default' is returned.
  • The value for key 4 is printed to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map3 = mapOf(1 to "apple", 2 to "banana", 3 to "cherry")
    val value3 = map3.getOrElse(4) { "default" }
    println(value3)
}

Output

default

Summary

In this Kotlin tutorial, we learned about getOrElse() extension function of Map: the syntax and few working examples with output and detailed explanation for each example.