mapNotNull
Returns a list containing only the non-null results of applying the given transform function to each character in the original char sequence.
import kotlin.test.*
fun main(args: Array<String>) {
//sampleStart
val strings: List<String> = listOf("12a", "45", "", "3")
val ints: List<Int> = strings.mapNotNull { it.toIntOrNull() }
println(ints) // [45, 3]
println(ints.sum()) // 48
//sampleEnd
}