How to Iterate Over Entries (Key-Value Pairs) in a Map in Kotlin - Step by Step Examples

How to Iterate Over Entries (Key-Value Pairs) in a Map in Kotlin ?

Answer

To iterate over entries (key-value pairs) in a map in Kotlin, you can use the entries property along with a for loop or the forEach method. This allows you to access each key-value pair in the map.

✐ Examples

1 Iterating Over Entries Using for Loop

We can iterate over entries in a map in Kotlin using a for loop with the entries property, which provides a convenient syntax for iterating over all key-value pairs in the map.

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 entries property to get a set of the key-value pairs in the map.
We iterate over the entries using a for loop, accessing each key and value directly from the set.
We print each key and value to the console using the println function to verify that we are iterating over all entries.

Kotlin Program

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

    // Iterate over entries using for loop
    for (entry in myMap.entries) {
        println("Key: ${entry.key}, Value: ${entry.value}")
    }
}

Output

Key: one, Value: 1
Key: two, Value: 2
Key: three, Value: 3

2 Iterating Over Entries Using forEach Method

We can iterate over entries in a map in Kotlin using the forEach method, which provides a flexible way to access each key-value pair in the map.

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 forEach method to iterate over the key-value pairs in the map.
In the lambda expression passed to forEach, we access each key and value.
We print each key and value to the console using the println function to verify that we are iterating over all entries.

Kotlin Program

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

    // Iterate over entries using forEach method
    myMap.forEach { (key, value) ->
        println("Key: $key, Value: $value")
    }
}

Output

Key: one, Value: 1
Key: two, Value: 2
Key: three, Value: 3

3 Storing and Iterating Over Entries Separately

We can store entries in a separate list and then iterate over the list in Kotlin, which provides a way to work with key-value pairs independently of the map.

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 declare a list named entries to store the key-value pairs from the map.
We use the entries property to get a set of the key-value pairs in the map and convert it to a list using the toList method.
We use a for loop to iterate over the entries list and print each key and value to the console using the println function to verify that we have stored all entries separately.

Kotlin Program

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

    // Store entries in a separate list
    val entries = myMap.entries.toList()

    // Iterate over the entries list
    for (entry in entries) {
        println("Key: ${entry.key}, Value: ${entry.value}")
    }
}

Output

Key: one, Value: 1
Key: two, Value: 2
Key: three, Value: 3

Summary

In this tutorial, we learned How to Iterate Over Entries (Key-Value Pairs) in a Map in Kotlin language with well detailed examples.

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How to Iterate Over Entries (Key-Value Pairs) in a Map in Kotlin - Step by Step Examples