I think it is clear that node is not null in the e...

# getting-started

[MaximilianH]

I think it is clear that node is not null in the else brach, but the compiler forces me to use ?. . Is there a better way to do this?

[Martin Benda]

Slightly unrelated, but you probably want node?.next = Node(content) instead of node?.content = content. As for the smart-cast to Node<T>, the compiler probably does not do it because of the node = node?.next assignment in the loop. You could use the !! operator instead of ?., but I'm not sure if there is a better way.

[Martin Benda]

fun push(content: T) {
        if (first == null) {
            first = Node(content)
        } else {
            var node = first!!
            while (node.next != null) {
                node = node.next!!
            }
            node.next = Node(content)
        }
    }}

[Edwar D Day]

I would expect, that the reason for the nullability is the mutability of fields. So you do a non null check on next, but don't know, if a different Thread or whatever changes the field again between check an assignment. You might solve this by introducing an intermediate local variable to hold the value, you check against.

class Stack<T> {
    private var first: Node<T>? = null

    fun push(content: T) {
        var h = first
        if (h == null) {
            first = Node(content)
        } else {
            var node = h
            h = h.next
            while (h != null) {
                node = h
            }
            node.content = content
        }
    }
}

class Node<T>(var content: T) {
	var next: Node<T>? = null
}