How to Set a Default Value for a Key in a Map in Kotlin - Step by Step Examples

How to Set a Default Value for a Key in a Map in Kotlin ?

Answer

To set a default value for a key in a map in Kotlin, you can use the getOrPut method, which inserts the key with a default value if the key does not already exist.

✐ Examples

1 Setting a Default Value Using getOrPut Method

We can set a default value for a key in a map in Kotlin using the getOrPut method, which inserts a key-value pair if the key does not already exist in the map.

For example,

We start by declaring and initializing a mutable map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We use the getOrPut method to set a default value for a key. The getOrPut method takes the key and a lambda that returns the default value to be inserted if the key is not already present in the map.
We print the updated map to the console using a for loop and println.

Kotlin Program

fun main() {
    // Declare and initialize a mutable map
    val myMap = mutableMapOf(
        "one" to 1,
        "two" to 2,
        "three" to 3
    )

    // Set a default value using getOrPut method
    myMap.getOrPut("four") { 4 }

    // Print the updated map
    for ((key, value) in myMap) {
        println("$key: $value")
    }
}

Output

one: 1
two: 2
three: 3
four: 4

2 Setting Multiple Default Values Using getOrPut Method

We can set multiple default values for keys in a map in Kotlin using the getOrPut method, which inserts key-value pairs if the keys do not already exist in the map.

For example,

We start by declaring and initializing a mutable map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We use the getOrPut method to set multiple default values for keys. The getOrPut method takes the key and a lambda that returns the default value to be inserted if the key is not already present in the map.
We print the updated map to the console using a for loop and println.

Kotlin Program

fun main() {
    // Declare and initialize a mutable map
    val myMap = mutableMapOf(
        "one" to 1,
        "two" to 2,
        "three" to 3
    )

    // Set multiple default values using getOrPut method
    myMap.getOrPut("four") { 4 }
    myMap.getOrPut("five") { 5 }

    // Print the updated map
    for ((key, value) in myMap) {
        println("$key: $value")
    }
}

Output

one: 1
two: 2
three: 3
four: 4
five: 5

3 Setting a Default Value Conditionally Using getOrPut Method

We can set a default value for a key in a map in Kotlin using the getOrPut method, which inserts a key-value pair if the key does not already exist in the map, based on a condition.

For example,

We start by declaring and initializing a mutable map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We use the getOrPut method to set a default value for a key based on a condition. The getOrPut method takes the key and a lambda that returns the default value to be inserted if the key is not already present in the map.
We print the updated map to the console using a for loop and println.

Kotlin Program

fun main() {
    // Declare and initialize a mutable map
    val myMap = mutableMapOf(
        "one" to 1,
        "two" to 2,
        "three" to 3
    )

    // Set a default value conditionally using getOrPut method
    myMap.getOrPut("four") { myMap["four"] ?: 4 }

    // Print the updated map
    for ((key, value) in myMap) {
        println("$key: $value")
    }
}

Output

one: 1
two: 2
three: 3
four: 4

Summary

In this tutorial, we learned How to Set a Default Value for a Key in a Map in Kotlin language with well detailed examples.

◀ Previous Next ▶

Kotlin Tutorials

Kotlin How-Tos

How to Set a Default Value for a Key in a Map in Kotlin - Step by Step Examples