Programming in Kotlin - Part 36: Mutable vs | Ray Wenderlich Videos

Official Tutorials
1

Learn the difference between the two types of collections.

This is a companion discussion topic for the original entry at https://www.raywenderlich.com/4736-programming-in-kotlin/lessons/36
2

I don’t know why, but IntelliJ is giving me an unresolved reference error when I try to declare an ArrayList as you did in the tutorial. I’ve tried using Alt+Enter to import it properly, but it didn’t make any difference.

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3

Have you tried to manually type the import? For example:
import kotlin.collections.ArrayList