How do I convert an array of Strings to an Array of Int in Kotlin

Question

I am looking to convert an List<String> to an List<Int> in Kotlin.

val stringArray = "1 2 3 4 5 6".split(" ")
val intArray = MutableList<Int>(0, {0})
for (item in stringArray) {
    intArray.add(item.toInt())
}

The above will do it, but it feels as if there is a better way of doing this (possible with lambdas and streams?).

Possible duplicate of How to convert String array to Int array in Kotlin? — CrazyApple
– CrazyApple, Commented Dec 4, 2017 at 13:53

s1m0nw1 · Accepted Answer · 2017-12-04 12:18:00Z

8

If your input really has delimiters, you can split as already suggested. Afterwards map is what you need. This will do the trick:

val numbers = "1 2 3 4 5 6"
val result = numbers.split(" ").map(String::toInt)

answered Dec 4, 2017 at 12:18

s1m0nw1

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RobCo · Accepted Answer · 2017-12-04 12:17:32Z

4

val intArray = stringArray.map(String::toInt)

or with lambda

val intArray = stringArray.map { it.toInt() }

answered Dec 4, 2017 at 12:17

RobCo

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2 Comments

Simon Featherstone Over a year ago

Great answers. But can you expand how they are different?

s1m0nw1 Over a year ago

They do the same with your array, it's just the type of parameter which defers: in the first example a method reference, in the second a lambda is passed to map

Ankit Patidar · Accepted Answer · 2017-12-04 15:00:22Z

2

You can use .map { ... } with .toInt() or .toIntOrNull():

 val result = strings.map { it.toInt() }

Only the result is not an array but a list. It is preferable to use lists over arrays in non-performance-critical code, see the differences.

If you need an array, add .toTypedArray() or .toIntArray().

answered Dec 4, 2017 at 15:00

Ankit Patidar

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