Kotlin Array - indexOf() Function

The Kotlin array indexOf() function returns first index if the element is present in an array otherwise it returns -1.

The first index suggests that if there are two elements with the same value, this function returns the index of the first one.

Syntax

Following is the syntax of Kotlin array indexOf() function −

fun <T> Array<out T>.indexOf(element: T): Int

Parameters

This function accepts element as parameters. Which represent an element which index need to be returned.

Return value

This function returns an index. Otherwise; -1.

Example 1

Following is the basic example to demonstrate the use of indexOf() function −

fun main(args: Array<String>){
   // let's create an array
   var array = arrayOf<Int>(1, 2, 3, 4, 5)
   // using indexOf
   val indx = array.indexOf(3)
   println("index of element 3: $indx")
}

Output

On execution of the above code we get the following result −

index of element 3: 2

Example 2

Now, let's see another example. Here, we use the indexOf() function to display an element. Otherwise, -1 if element is not available in an array −

fun main(args: Array<String>){
   // let's create an array
   var array = arrayOf<String>("tutorialspoint", "India", "tutorix", "India")
   val indx = array.indexOf("tutorials point")
   print("index of element: $indx")
}

Output

After execution of the above code we get the following output −

index of element: -1

Example 3

The below example creates an array. We then use indexOf function. If statement will be displayed if the element is not available in the array; otherwise, the else statement will be displayed. −

fun main(args: Array<String>){
   // let's create an array
   var array = arrayOf<Int>(1, 2, 3, 4, 5)
   // using indexOf
   val indx = array.indexOf(6)
   if(indx == -1){
      println("the element is not available in the array!")
   }else{
      println("element found at index: $indx")
   }   
}

Output

The above code produce following output −

the element is not available in the array!