How to Update the Value for a Key in a Map in Kotlin

How to Update the Value for a Key in a Map in Kotlin ?

Answer

To update the value for a key in a map in Kotlin, you can use the subscript operator or the put method. These methods allow you to modify the value associated with a specific key directly.

✐ Examples

1 Updating the Value Using Subscript Operator

We can update the value for a key in a map in Kotlin using the subscript operator, which allows us to modify the value associated with a specific key directly.

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 subscript operator to update the value for a specific key in the map. The subscript operator allows us to assign a new value to the key.
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
    )

    // Update the value using subscript operator
    myMap["two"] = 22

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

Output

one: 1
two: 22
three: 3

2 Updating the Value Using put Method

We can update the value for a key in a map in Kotlin using the put method, which allows us to modify the value associated with a specific key directly.

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 put method to update the value for a specific key in the map. The put method takes the key and the new value to be assigned.
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
    )

    // Update the value using put method
    myMap.put("two", 22)

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

Output

one: 1
two: 22
three: 3

3 Updating the Value Conditionally Using putIfAbsent Method

We can update the value for a key in a map in Kotlin using the putIfAbsent method, which allows us to modify the value only if the key does not already exist.

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 putIfAbsent method to conditionally update the value for a specific key in the map. The putIfAbsent method takes the key and the new value to be assigned, only if the key does not already exist.
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
    )

    // Update the value conditionally using putIfAbsent method
    myMap.putIfAbsent("two", 22)

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

Output

one: 1
two: 2
three: 3

Summary

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

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