removeFirst method
override
Removes and returns the element with the highest priority.
Repeatedly calling this method, without adding element in between,
is guaranteed to return elements in non-decreasing order as, specified by
the comparison
constructor parameter.
The queue must not be empty when this method is called.
Implementation
@override
E removeFirst() {
if (_length == 0) throw StateError('No element');
_modificationCount++;
var result = _elementAt(0);
var last = _removeLast();
if (_length > 0) {
_bubbleDown(last, 0);
}
return result;
}