Initializing Array from input stream in Kotlin

Question

I would like to read the next n integer from the input stream into an IntArray.

I wrote the code below but as we discussed in Order of init calls in Kotlin Array initialization there is no guarantee that the initialization would start from index 0 and go one by one.

Is there some similarly elegant solution for this which is not based on this possibly false (but as discussed in the other thread in all known implementations true) assumption?

fun Scanner.readIntArray(n: Int): IntArray {
    return IntArray(n){nextInt()}
}

Slaw · Accepted Answer · 2019-05-17 20:51:29Z

3

You could always iterate over the indices yourself to guarantee the behavior you want.

fun Scanner.readIntArray(n: Int) = IntArray(n).apply {
    for (i in 0 until size) {
        this[i] = nextInt()
    }
}

edited May 17, 2019 at 20:51

answered May 17, 2019 at 20:43

Slaw

49.9k8 gold badges65 silver badges109 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Ilya · Accepted Answer · 2019-10-02 01:46:15Z

2

Since the version 1.3.50 there's a guarantee in the API documentation that array elements are initialized sequentially. Therefore, you can use the original code from the question to populate an IntArray this way.

https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int-array/-init-.html

answered Oct 2, 2019 at 1:46

Ilya

23.3k9 gold badges79 silver badges96 bronze badges

Comments

Venkatesh-Prasad Ranganath · Accepted Answer · 2019-05-17 20:43:47Z

0

You could do return (1..n).map { nextInt() }.toIntArray().

answered May 17, 2019 at 20:43

Venkatesh-Prasad Ranganath

1,91614 silver badges20 bronze badges

1 Comment

Slaw Over a year ago

Note this results in a temporary List<Int> being created (which involves boxing).

Collectives™ on Stack Overflow

Initializing Array from input stream in Kotlin

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related