Are lists in Kotlin random access data structure and is it the same case for the list in Java? Also, how does one verify if the list in random-access collection or not practically through code sample?

List<T>

can't be said to be an random access structure There are several different implementations of this interface, notably

ArrayList<T>

(random access) and

LinkedList<T>

(NOT random access - `get(i)`/`[i]` are linear in time for linked list)

Kotlin provides the interface

RandomAccess

which you can use to check whether a list supports fast index based access.

(same as Java)

I’ve always seen the use of LinkedList as a code smell for premature optimization 🙂

"listOf()", the return value of ".map{}", etc. return a random access list

agreed that LinkedList is a low-key code smell. it's useful for queue-type things where you're popping things off the front a lot, but often there are better alternatives (like ArrayDeque)