Problem

package tutorial

class Node(newCargo: Int) {
    var cargo = newCargo
    var next: Node = null

    def add(newCargo: Int) {
        next = new Node(newCargo)
    }

    def getNext(): Node = {
        return next
    }
}

class LinkedList() {
    var head = null
    var tail = null
    var length = 0

    def pushBack(newCargo: Int) {
        tail.add(new) // Line 22
        tail = tail.next
    }
}