removeFirst method

V? removeFirst()

Implementation

V? removeFirst() {
  if (_queues.isEmpty) return null;
  final entry = _queues.entries.firstOrNull;
  if (entry == null) return null;
  final List<V> q = entry.value;
  final V v = q.removeAt(0);
  final K key = entry.key;
  if (q.isEmpty) _queues.remove(key);
  return v;
}