How to Check if a Key Exists in a Map in Kotlin

How to Check if a Key Exists in a Map in Kotlin ?

Answer

To check if a key exists in a map in Kotlin, you can use the containsKey method. This method returns a boolean value indicating whether the map contains the specified key.

✐ Examples

1 Checking if a Key Exists Using containsKey Method

We can check if a key exists in a map in Kotlin using the containsKey method, which returns true if the map contains the specified key and false otherwise.

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 containsKey method to check for a specific key in the map. The containsKey method returns a boolean value indicating whether the map contains the specified key.
We print the result to the console using the println function.

Kotlin Program

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

    // Check if a key exists using containsKey method
    val keyExists = myMap.containsKey("two")

    // Print the result
    println("Does key 'two' exist? $keyExists")
}

Output

Does key 'two' exist? true

2 Checking if a Key Does Not Exist Using containsKey Method

We can check if a key does not exist in a map in Kotlin using the containsKey method, which returns false if the map does not contain the specified key.

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 containsKey method to check for a specific key in the map. The containsKey method returns a boolean value indicating whether the map contains the specified key.
We print the result to the console using the println function.

Kotlin Program

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

    // Check if a key does not exist using containsKey method
    val keyExists = myMap.containsKey("four")

    // Print the result
    println("Does key 'four' exist? $keyExists")
}

Output

Does key 'four' exist? false

3 Checking Multiple Keys Using containsKey Method

We can check if multiple keys exist in a map in Kotlin using the containsKey method, which returns true if the map contains the specified key and false otherwise.

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 containsKey method to check for multiple keys in the map. The containsKey method returns a boolean value indicating whether the map contains the specified key.
We print the results to the console using the println function.

Kotlin Program

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

    // Check if multiple keys exist using containsKey method
    val keyExistsOne = myMap.containsKey("one")
    val keyExistsFour = myMap.containsKey("four")

    // Print the results
    println("Does key 'one' exist? $keyExistsOne")
    println("Does key 'four' exist? $keyExistsFour")
}

Output

Does key 'one' exist? true
Does key 'four' exist? false

Summary

In this tutorial, we learned How to Check if a Key Exists in a Map in Kotlin language with well detailed examples.

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