single
Returns the single character, or throws an exception if the char sequence is empty or has more than one character.
fun CharSequence.single(): Char(source)
val singleChar = "A".single()
println(singleChar) // prints: A
try {
"AB".single() // throws NoSuchElementException
} catch (e: NoSuchElementException) {
println("Exception: ${e.message}")
}