How can use filter and contains with multi-ArrayList in Kotlin so I only have elements which match the condition? I have a class called Person data class Person( val id: Int, val name: String ) data class IDs( val id : Int, val active : Boolean ) and an array list that has numbers of ids and another list of Persons val myStu = listOf(Person(1, "Name_1"), Person(2, "Name_2"), Person(3, "Name_3")) var ids = listOf(IDs(1,false),IDs(2,true),IDs(3,true)) var newIds = listOf(2,3,4,6) First I want to apply two actions to the myStu, first is to have a list that include all the items from myStu...