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How to use the firstOrNull() method of ArrayDeque in Kotlin
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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");
}Using the firstOrNull method
Explanation
-
Line 3: We create a new
ArrayDequewith the namedeque. It contains no element[]. -
Line 7: We use the
firstOrNullmethod to get the first element ofdeque. In our case, the array is empty, so it returnsnull. -
Lines 11–14: We use the
addmethod to add four elements todeque. Now,dequehas[1,2,3,4]. -
Line 18: We use the
firstOrNullmethod to get the deque’s first element,1. This array is not empty, so the first element of thedequeis returned.
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kotlin
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