How to Sort a Map by Values in Kotlin - Step by Step Examples

How to Sort a Map by Values in Kotlin ?

Answer

To sort a map by values in Kotlin, you can convert the map entries to a list, sort the list by values, and then convert it back to a map. This method allows you to sort the map based on values.

✐ Examples

1 Sorting a Map by Values Using List Conversion

We can sort a map by values in Kotlin by converting the map entries to a list, sorting the list by values, and then converting it back to a map.

For example,

We start by declaring and initializing a map named unsortedMap with some key-value pairs. In this example, the map has string keys and integer values.
We convert the map entries to a list and sort the list by values using the sortedBy function.
We create a new map from the sorted list of map entries using the toMap function.
We print the sorted map to the console using the println function to verify the sorting.

Kotlin Program

fun main() {
    // Declare and initialize an unsorted map
    val unsortedMap = mapOf("apple" to 3, "banana" to 1, "cherry" to 2)

    // Convert the map entries to a list and sort the list by values
    val sortedEntries = unsortedMap.entries.sortedBy { it.value }

    // Create a new map from the sorted list of map entries
    val sortedMap = sortedEntries.toMap()

    // Print the sorted map
    println("Sorted Map by Values: $sortedMap")
}

Output

Sorted Map by Values: {banana=1, cherry=2, apple=3}

2 Sorting a Map by Values in Descending Order

We can sort a map by values in descending order in Kotlin by converting the map entries to a list, sorting the list by values in descending order, and then converting it back to a map.

For example,

We start by declaring and initializing a map named unsortedMap with some key-value pairs. In this example, the map has string keys and integer values.
We convert the map entries to a list and sort the list by values in descending order using the sortedByDescending function.
We create a new map from the sorted list of map entries using the toMap function.
We print the sorted map to the console using the println function to verify the sorting.

Kotlin Program

fun main() {
    // Declare and initialize an unsorted map
    val unsortedMap = mapOf("apple" to 3, "banana" to 1, "cherry" to 2)

    // Convert the map entries to a list and sort the list by values in descending order
    val sortedEntries = unsortedMap.entries.sortedByDescending { it.value }

    // Create a new map from the sorted list of map entries
    val sortedMap = sortedEntries.toMap()

    // Print the sorted map
    println("Sorted Map by Values (Descending): $sortedMap")
}

Output

Sorted Map by Values (Descending): {apple=3, cherry=2, banana=1}

3 Sorting a Map with Numeric Keys by Values

We can sort a map with numeric keys by values in Kotlin by converting the map entries to a list, sorting the list by values, and then converting it back to a map.

For example,

We start by declaring and initializing a map named unsortedMap with some key-value pairs. In this example, the map has integer keys and string values.
We convert the map entries to a list and sort the list by values using the sortedBy function.
We create a new map from the sorted list of map entries using the toMap function.
We print the sorted map to the console using the println function to verify the sorting.

Kotlin Program

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

    // Convert the map entries to a list and sort the list by values
    val sortedEntries = unsortedMap.entries.sortedBy { it.value }

    // Create a new map from the sorted list of map entries
    val sortedMap = sortedEntries.toMap()

    // Print the sorted map
    println("Sorted Map by Values: $sortedMap")
}

Output

Sorted Map by Values: {1=one, 2=two, 3=three}

Summary

In this tutorial, we learned How to Sort a Map by Values in Kotlin language with well detailed examples.

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How to Sort a Map by Values in Kotlin - Step by Step Examples