How to Convert a Map to an Array of Keys in Kotlin

How to Convert a Map to an Array of Keys in Kotlin ?

Answer

To convert a map to an array of keys in Kotlin, you can use the keys property to get a set of keys and then convert this set to a list. This provides a convenient way to extract all keys from the map.

✐ Examples

1 Converting a Map to an Array of Keys Using keys Property

We can convert a map to an array of keys in Kotlin using the keys property, which provides a set of all keys in the map. We can then convert this set to a list.

For example,

We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We use the keys property to get a set of the keys in the map.
We convert the set of keys to a list using the toList method.
We store the list of keys in a variable named keysList.
We print the list of keys to the console using the println function to verify the conversion.

Kotlin Program

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

    // Convert map to an array of keys
    val keysList = myMap.keys.toList()

    // Print the keys
    println("Keys: $keysList")
}

Output

Keys: [one, two, three]

2 Converting an Empty Map to an Array of Keys

We can also convert an empty map to an array of keys in Kotlin using the keys property, which returns an empty list when the map is empty.

For example,

We start by declaring an empty map named emptyMap with string keys and integer values.
We use the keys property to get a set of the keys in the empty map.
We convert the set of keys to a list using the toList method.
We store the list of keys in a variable named emptyKeysList.
We print the list of keys to the console using the println function to verify that the list is empty.

Kotlin Program

fun main() {
    // Declare an empty map
    val emptyMap = mapOf<String, Int>()

    // Convert empty map to an array of keys
    val emptyKeysList = emptyMap.keys.toList()

    // Print the keys
    println("Keys: $emptyKeysList")
}

Output

Keys: []

3 Converting a Map to an Array of Keys After Adding Elements

We can convert a map to an array of keys in Kotlin after adding elements using the keys property, which provides an updated set of all keys in the map.

For example,

We start by declaring an empty mutable map named dynamicMap with string keys and integer values.
We add some key-value pairs to the map using the map's index notation.
We use the keys property to get a set of the keys in the map after adding elements.
We convert the set of keys to a list using the toList method.
We store the list of keys in a variable named dynamicKeysList.
We print the list of keys to the console using the println function to verify the updated list of keys.

Kotlin Program

fun main() {
    // Declare an empty mutable map
    val dynamicMap = mutableMapOf<String, Int>()

    // Add elements to the map
    dynamicMap["one"] = 1
    dynamicMap["two"] = 2
    dynamicMap["three"] = 3

    // Convert map to an array of keys after adding elements
    val dynamicKeysList = dynamicMap.keys.toList()

    // Print the keys
    println("Keys: $dynamicKeysList")
}

Output

Keys: [one, two, three]

Summary

In this tutorial, we learned How to Convert a Map to an Array of Keys in Kotlin language with well detailed examples.

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