Removes all elements in the queue. The size of the queue becomes zero.
void clear() {
  _sentinel._nextLink = _sentinel;
  _sentinel._previousLink = _sentinel;
  _elementCount = 0;
}
    © 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/clear.html