Why does line 6 still prints "A" here, see <https:...

# announcements

[torres]

Why does line 6 still prints "A" here, see https://stackoverflow.com/questions/62595494/linkedlist-remove-element-puzzle

fun main(args: Array<String>) {
        var tree = Node("A", null, null)
        val q: Queue<Node> = LinkedList()
        q.add(tree)
        tree = q.remove() // line 5, remove element in q and assign to tree so tree so should size 0
        println(tree.data) // line 6, why does this still print "A" though?
}
// given
class Node {
    var data: String
    var left: Node? = null
    var right: Node? = null

    constructor(data: String) {
        this.data = data
    }

    constructor(data: String, left: Node?, right: Node?) {
        this.data = data
        this.left = left
        this.right = right
    }
}

[diesieben07]

You only ever create one Tree object. You put it into the queue and then get it back out, but it's still the same Node object

[torres]

huh? im still confuse. does this mean this line does nothing then? tree = q.remove() // line 5

[diesieben07]

Well it removes the first element from the list, which happens to be the same as tree. So what it does is change the list contents

[diesieben07]

But it does not change the object thats stored in tree

[Michael de Kaste]

you create Node and name it tree
you make a list
you put the node (tree) in the list
you remove the node(tree) and assign that node to tree (tree = tree)

[Michael de Kaste]

so yeah, q.remove() removes a node from it's queue, but returns it for you. and you assigned that into your var tree

[torres]

yea tree is declared as var so it should take the content of q.remove()

[torres]

and q.remove() removed the content

[Michael de Kaste]

and returns that content

[torres]

so tree shoudl have no content?

[Michael de Kaste]

no you dont understand

[Michael de Kaste]

look what the q.remove() statement does

[torres]

yea

[torres]

i see

[torres]

i missed the bit that said return removeFirst();

[torres]

thanks