Find last occurrence of a String in array using Kotlin

For your question of finding the first and last occurrences in an Array there is no need to use a for-loop at all in Kotlin, you can simply use indexOf and lastIndexOf

As for throwing an error you can throw an Exception if indexOf returns -1, observe:

import java.util.Arrays

fun main(args: Array<String>) {
  // Declaring array
  val wordArray = arrayOf("cat", "dog", "lion", "tiger", "dog", "rabbit")

  // Declaring search word
  var searchWord = "dog"

  // Finding position of first occurence
  var firstOccurence  = wordArray.indexOf(searchWord)

  // Finding position of last occurence
  var lastOccurence = wordArray.lastIndexOf(searchWord)

  println(Arrays.toString(wordArray))

  println("\"$searchWord\" first occurs at index $firstOccurence of the array")

  println("\"$searchWord\" last occurs at index $lastOccurence of the array")

  // Testing something that does not occur in the array
  searchWord = "bear"
  var index = wordArray.indexOf(searchWord)
  if (index == -1) throw Exception("Error: \"$searchWord\" does not occur in the array")
}

Output

[cat, dog, lion, tiger, dog, rabbit]
"dog" first occurs at index 1 of the array
"dog" last occurs at index 4 of the array
java.lang.Exception: Error: "bear" does not occur in the array