private fun maxSubListSum(list: List<Int>, n: Int): Int? {
    if (list.isEmpty()) {
        return null
    }

    var max: Int? = null

    (0..list.size - n).forEach { i ->
        var temp: Int? = null
        (i until (i + n)).forEach { j ->
            if (temp == null) {
                temp = list[j]
            } else {
                temp?.let { temp = it + list[j] }
            }
        }

        temp?.let { localTemp ->
            if(max == null) {
                max = localTemp
            } else {
                max?.let { localMax ->
                    if(localTemp > localMax) {
                        max = temp
                    }
                }
            }
        }
    }

    return max
}

temp

max

Int?

temp

max

let

temp?.let { localTemp ->
            if(max == null) {
                max = localTemp
            } else {
                max?.let { localMax ->
                    if(localTemp > localMax) {
                        max = temp
                    }
                }
            }
        }

let

if(temp == null)

temp

Int

Int.MIN_VALUE

null

temp

Int

null

forEach

for

forEach

?.let {}

if (x != null) {}

Unit

StateFlow

data class State(val isLoading: Boolean, val name: String?)

fun main() {
    val mutableStateFlow = MutableStateFlow(State(false, null))
    val stateFlow = mutableStateFlow as StateFlow<State>

    val scope1 = CoroutineScope(Job())
    val scope2 = CoroutineScope(Job())

    scope1.launch {
        delay(1000)
        mutableStateFlow.value = State(true, null)
        mutableStateFlow.value = State(false, "name")
    }

    scope2.launch {
        stateFlow.collect {
            println("value = $it")
        }
    }
    Thread.sleep(2000)
}

State(true, null)

State(false, name)

@DeprecatedSinceKotlin("1.4")

data class Foo(val id: String? = null)

val list = listOf(Foo("0"), Foo(), Foo("2"))

// I would like to get ["0", "2"]
// I use this, but I don't like the Double !! 
list.filter { it.id != null }
    .map { it.id!! }

list.mapNotNull { it.id }