CODEWITHSUNDEEP
kotlinjava-stream
Whitecat
Whitecat

Reputation: 4020

How to convert a map to a map kotlin

How can I convert a Map<String, ArrayList<Int>> to a Map<String, Int>?

My objects are as follows:

val mapOfItems = mapOf("x" to listOf(1, 2), "y" to listOf(1, 3), "z" to listOf(2, 3))

I want to get an object like this:

val mapOfSummedItems = mapOf("x" to 3, "y" to 4, "z" to 5)

I tried:

mapOfItems.map { (key, value) -> SummedItems(key, value.sum()) }
                .groupBy { it.key }

data class SummedItems(val key: String, val sum: Int)

That does not give me what I want that gives me an Map<String, ArrayList<SummedItems>>

Upvotes: 0

Views: 490

Answers (1)

Joe
Joe

Reputation: 607

.map() on a Map generates a List. While you can make this a List<Pair> and then use associate* operators to get back into a Map, you can also just map the values directly:

mapOfItems.mapValues { it.value.sum() }

Upvotes: 4

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