Returns the first element.
Throws a StateError if this is empty. Otherwise returns the first element in the iteration order, equivalent to this.elementAt(0).
E get first {
  _DoubleLinkedQueueEntry<E> firstEntry = _sentinel._nextLink;
  return firstEntry._element;
}
    © 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
    https://api.dart.dev/stable/2.5.0/dart-collection/DoubleLinkedQueue/first.html