The
kotlin.collections
package is part of Kotlin’s standard library, and it contains all collection types, such asMap
,List
,Set
, etc. The package provides theArrayList
class, a mutable list, and uses a dynamically resizable array as the backing storage.
The ArrayList
class contains the lastIndexOf()
method, which returns the index of the last occurrence of the specified element in the list and -1 if the element is not present in the list.
fun lastIndexOf(element: E): Int
ArrayList
follows the sequence of insertion of elements.
It is allowed to contain duplicate elements.
The illustration below shows the function of the lastIndexOf()
method.
fun main(args : Array<String>) {val sportsList = ArrayList<String>()sportsList.add("Cricket")sportsList.add("Football")sportsList.add("Tennis")sportsList.add("Football")sportsList.add("Racing")println("Printing ArrayList elements --")println(sportsList)var lastIndex = sportsList.lastIndexOf("Football")println("Last Index of 'Football' is ${lastIndex}")lastIndex = sportsList.lastIndexOf("Hockey")println("Last Index of 'Hockey' is ${lastIndex}")}
Line 2: We create an empty array list named sportsList
to store the strings.
Line 4 to 7: We add a few sport names to the ArrayList
object using the add()
method, such as: "Cricket"
, "Football"
, "Tennis"
, "Football"
, and "Racing"
.
Line 11: We call the lastIndexOf()
method and pass the input string as "Football"
. It returns 3 as "Football"
exists twice, first at index 1 and last at index 3 in the list.
Line 13: We call the lastIndexOf()
method and pass the input string as "Hockey"
. It returns -1, as "Hockey"
does not exist in the list.
The ArrayList
elements and result of the lastIndexOf()
method are displayed using the println()
function of the kotlin.io
package.