Kotlin Map asSequence()
Syntax & Examples

Syntax of Map.asSequence()

The syntax of Map.asSequence() extension function is:

fun <K, V> Map<out K, V>.asSequence(): Sequence<Entry<K, V>>

This asSequence() extension function of Map creates a Sequence instance that wraps the original map returning its entries when being iterated.

✐ Examples

1 Map as Sequence of Entries

In this example,

We create a map named map1 with integer keys and string values.
We use the asSequence extension function to convert the map into a sequence of key-value pairs (entries).
We iterate over the sequence using forEach and print each entry to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map1 = mapOf(1 to "one", 2 to "two", 3 to "three");
    val sequence = map1.asSequence();
    sequence.forEach { println(it) };
}

Output

1=one
2=two
3=three

2 Map as Sequence of Entries

In this example,

We create a map named map2 with string keys and integer values.
We use the asSequence extension function to convert the map into a sequence of key-value pairs (entries).
We iterate over the sequence using forEach and print each entry to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map2 = mapOf("a" to 1, "b" to 2, "c" to 3);
    val sequence = map2.asSequence();
    sequence.forEach { println(it) };
}

Output

a=1
b=2
c=3

3 Map as Sequence of Entries

In this example,

We create a map named map3 with string keys and integer values.
We use the asSequence extension function to convert the map into a sequence of key-value pairs (entries).
We iterate over the sequence using forEach and print each entry to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val map3 = mapOf("apple" to 5, "banana" to 6, "cherry" to 7);
    val sequence = map3.asSequence();
    sequence.forEach { println(it) };
}

Output

apple=5
banana=6
cherry=7

Summary

In this Kotlin tutorial, we learned about asSequence() extension function of Map: the syntax and few working examples with output and detailed explanation for each example.