Create an empty queue.
If initialCapacity is given, prepare the queue for at least that many
elements.
Source
ListQueue([int initialCapacity]) : _head = 0, _tail = 0 {
if (initialCapacity == null || initialCapacity < _INITIAL_CAPACITY) {
initialCapacity = _INITIAL_CAPACITY;
} else if (!_isPowerOf2(initialCapacity)) {
initialCapacity = _nextPowerOf2(initialCapacity);
}
assert(_isPowerOf2(initialCapacity));
_table = new List<E>(initialCapacity);
}