How to use the firstOrNull() method of ArrayDeque in Kotlin

Overview

In Kotlin, the firstOrNull() method is used to get the first element of ArrayDeque.

Syntax

fun firstOrNull(): E?

Parameter

This method doesn’t take any argument.

Return value

This method returns the first element if the ArrayDeque is not empty. Otherwise, it returns null.

Example

fun main() {

    // create a new empty ArrayDeque which can have int elements

    var deque = ArrayDeque<Int>()



    println("The Arraydeque is $deque")

    // get the first element of deque

    var firstEle = deque.firstOrNull();

    println("The First element is $firstEle");

    

    // add four elements to deque

    deque.add(1)

    deque.add(2)

    deque.add(3)

    deque.add(4)

    println("\nThe Arraydeque is $deque")



    // get the first element of deque

    firstEle = deque.firstOrNull();

    println("The First element is $firstEle");

}

Explanation

  • Line 3: We create a new ArrayDeque with the name deque. It contains no element [].

  • Line 7: We use the firstOrNull method to get the first element of deque. In our case, the array is empty, so it returns null.

  • Lines 11–14: We use the add method to add four elements to deque. Now, deque has [1,2,3,4].

  • Line 18: We use the firstOrNull method to get the deque’s first element, 1. This array is not empty, so the first element of the deque is returned.

Free AI Mock Interviews
Coding Interview
Coding PatternsFree Interview
Gain insights and practical experience with coding patterns through targeted MCQs and coding problems, designed to match and challenge your expertise level.
System Design
You TubeFree Interview
Learn to design a video streaming platform like YouTube by tackling functional and non-functional requirements, core components, and high-level to detailed design challenges.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)