addFirst method

void addFirst(T obj)

Adds a node to the beginning of the list.

Implementation

void addFirst(T obj) {
  _Node<T> newNode = _Node(obj);
  newNode.next = _head;
  newNode.previous = null;
  if (_head != null) _head!.previous = newNode;
  _head = newNode;
  if (_tail == null) _tail = newNode;
  _size++;
}