kotlin val numbers: List<Int> = listOf(1, 2, 3, 4, 5) val doubledNumbers: List<Int> = numbers.map { it * 2 } kotlin fun String.trimToNull(): String? { val trimmed = trim() return if (trimmed.isEmpty()) null else trimmed } kotlin val str: String? = null val length: Int? = str?.length kotlin val file = File("path/to/file.txt") file.bufferedReader().use { reader -> val content: String = reader.readText() }