Hi there :slightly_smiling_face: I found an Issue ...

# stdlib

[Aljoscha Burgmaier]

Hi there 🙂
I found an Issue on YouTrack closed in 2018, where there was a discussion to include the Collection utils functionalities into the standard lib: https://youtrack.jetbrains.com/issue/KT-2460/Provide-java.util.Collections-methods-as-extensions-for-collections

I needed for a Project the swap and the and the toSynchonized from the Java utils. The swap I created smaller utilities to be able to swap an element within a MutableList and to retrieve a copy of a List with the swapped elements.

I had the idea to crate a PR to provide swap functionalities in Kotlin, what do you think?

I also discovered that you can swap elements within a normal List with the Collection utils. Is that a Bug?

import java.util.Collections

val list = listOf("A", "B", "C")

println(list) // [A, B, C]
Collections.swap(list, 0, 2)
println(list) // [C, B, A]

[Klitos Kyriacou]

Looks like an existing feature request:
https://youtrack.jetbrains.com/issue/KT-33768/Add-Collection.swap-extension-to-stdlib

I think what you discovered and asked if it's a bug, is something unavoidable. I can't think of a way to prevent it.

[Aljoscha Burgmaier]

Thank you 🙂 Yes there it it also denied for getting into the core. Is it so uncommon to use a swap? What would be an alternative?

The only way to prevent that, I could think of, would be an unmodifiable List, that prevents to use set. But I don't think that would work reliable.