Kotlin List lastIndexOf()
Syntax & Examples

Syntax of List.lastIndexOf()

The syntax of List.lastIndexOf() function is:

abstract fun lastIndexOf(element: E): Int

This lastIndexOf() function of List returns the index of the last occurrence of the specified element in the list, or -1 if the specified element is not contained in the list.

✐ Examples

1 Example

In this example,

We create a list named list1 containing the elements 'a', 'b', 'c', 'b', 'a'.
We find the index of the last occurrence of 'b' using the List lastIndexOf() function, which returns the index of the last occurrence of the specified element.
The last occurrence of 'b' is at index 3 in list1, so lastIndexB will be 3.
Finally, we print the value of lastIndexB to standard output using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val list1 = listOf("a", "b", "c", "b", "a")
    val lastIndexB = list1.lastIndexOf("b")
    println(lastIndexB)
}

Output

2 Example

In this example,

We create a list named list2 containing the integers 10, 20, 30, 20, 40.
We find the index of the last occurrence of 20 using the List lastIndexOf() function, which returns the index of the last occurrence of the specified element.
The last occurrence of 20 is at index 3 in list2, so lastIndex20 will be 3.
Finally, we print the value of lastIndex20 to standard output using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val list2 = listOf(10, 20, 30, 20, 40)
    val lastIndex20 = list2.lastIndexOf(20)
    println(lastIndex20)
}

Output

3 Example

In this example,

We create a list named list3 containing the elements 'apple', 'banana', 'cherry', 'banana', 'date'.
We try to find the index of the last occurrence of 'grape' using the List lastIndexOf() function, which returns the index of the last occurrence of the specified element.
Since 'grape' is not present in list3, lastIndexOf() returns -1.
Finally, we print the value of lastIndexGrape to standard output using the println function.

Kotlin Program

fun main(args: Array<String>) {
    val list3 = listOf("apple", "banana", "cherry", "banana", "date")
    val lastIndexGrape = list3.lastIndexOf("grape")
    println(lastIndexGrape)
}

Output

-1

Summary

In this Kotlin tutorial, we learned about lastIndexOf() function of List: the syntax and few working examples with output and detailed explanation for each example.