public void add(T element) {
        if(size == 0) {
            root = new Node<T>(element); //if the tree is empty, element = root
            size++;
        return;
        }
            if(contains(element)) {
                return;
            }
            Node<T> currentNode = root;
            int temp = currentNode.data.compareTo(element);
            while(currentNode != null) {
                if(temp == -1) { //currentNode < element
                if(currentNode.right == null) {
                        currentNode.right = new Node<T>(element); //this is where the element is put in the tree (if the tree was not empty)
                    size++;
                    break; //går ut ur while-loopen
                }
                    currentNode = currentNode.right;
                }
                    if(temp == 1) { //currentNode > element
                        if(currentNode.left == null) {
                        currentNode.left = new Node<T>(element); //this is where the element is put in the tree (if the tree was not empty)
                    size++;
                    break;
                }
            currentNode = currentNode.left;
                }
                temp = currentNode.data.compareTo(element);
            }
    }