singleOrNull
Returns single element, or null if the array is empty or has more than one element.
fun <T> Array<out T>.singleOrNull(): T?(source)
fun main() {
val singleArray = arrayOf(10)
println(singleArray.singleOrNull()) // prints: 10
val multipleArray = arrayOf(1, 2)
println(multipleArray.singleOrNull()) // prints: null
val emptyArray = arrayOf<Int>()
println(emptyArray.singleOrNull()) // prints: null
}