Difference between List.subList and slice in Kotlin - list

Question

I recently realised there are two very similar functions in Kotlin for getting a portion of a List, but I'm unsure of the difference:
The documentation for List.subList says:
Returns a view of the portion of this list between the specified fromIndex (inclusive) and toIndex (exclusive). The returned list is backed by this list, so non-structural changes in the returned list are reflected in this list, and vice-versa.
Structural changes in the base list make the behavior of the view undefined.
whereas the documentation for slice says:
Returns a list containing elements at indices in the specified indices range.
Or
Returns a list containing elements at specified indices.
It seems that the key differences are that the first one returns a "view of the portion" of the list, and whether non-structural changes are reflected? However I'm not quite sure what this means.
I looked at the source code for the slice function:
public fun <T> List<T>.slice(indices: IntRange): List<T> {
if (indices.isEmpty()) return listOf()
return this.subList(indices.start, indices.endInclusive + 1).toList()
}
But it returns a list from the subList function.
Could someone explain the differences between these two functions and when you might want to use one over the other?

Answer 1

The key in List<T>.slice function is the .toList() at the end.
The call to toList() will create a new List with all the elements, like a copy.
For summary:
.slice() will create a new List with the subset of elements
.subList() is only a view of the original List that will change with it.
You can see differences here: https://pl.kotl.in/-JU8BDNZN
fun main() {
val myList = mutableListOf(1, 2, 3, 4)
val subList = myList.subList(1, 3)
val sliceList = myList.slice(1..2)
println(subList) // [2, 3]
println(sliceList) // [2, 3]
myList[1] = 5
println(subList) // [5, 3]
println(sliceList) // [2, 3]
}