description

# Queue<E> class abstract interface

A Queue is a collection that can be manipulated at both ends. One can iterate over the elements of a queue through forEach or with an Iterator.

It is generally not allowed to modify the queue (add or remove entries) while an operation in the queue is being performed, for example during a call to forEach. Modifying the queue while it is being iterated will most likely break the iteration. This goes both for using the iterator directly, or for iterating an `Iterable` returned by a method like map or where.

Example:

    final queue = Queue<int>(); // ListQueue() by default
    print(queue.runtimeType); // ListQueue

    // Adding items to queue
    queue.addAll([1, 2, 3]);
    queue.addFirst(0);
    queue.addLast(10);
    print(queue); // {0, 1, 2, 3, 10}

    // Removing items from queue
    queue.removeFirst();
    queue.removeLast();
    print(queue); // {1, 2, 3}

Implemented types
  - Iterable<E>
Implementers
  - DoubleLinkedQueue
  - ListQueue
Available extensions
  - EnumByName
  - FutureIterable
  - IterableExtensions
  - IterableToJSIterable
  - NullableIterableExtensions

## Constructors

Queue()
  Creates a queue.
  factory
Queue.from(Iterable elements)
  Creates a queue containing all `elements`.
  factory
Queue.of(Iterable<E> elements)
  Creates a queue from `elements`.
  factory

## Properties

first → E
  The first element.
  no setterinherited
firstOrNull → T?

  Available on Iterable<T>, provided by the IterableExtensions extension

  The first element of this iterator, or `null` if the iterable is empty.
  no setter
hashCode → int
  The hash code for this object.
  no setterinherited
indexed → Iterable<(int, T)>

  Available on Iterable<T>, provided by the IterableExtensions extension

  Pairs of elements of the indices and elements of this iterable.
  no setter
isEmpty → bool
  Whether this collection has no elements.
  no setterinherited
isNotEmpty → bool
  Whether this collection has at least one element.
  no setterinherited
iterator → Iterator<E>
  A new `Iterator` that allows iterating the elements of this `Iterable`.
  no setterinherited
last → E
  The last element.
  no setterinherited
lastOrNull → T?

  Available on Iterable<T>, provided by the IterableExtensions extension

  The last element of this iterable, or `null` if the iterable is empty.
  no setter
length → int
  The number of elements in this Iterable.
  no setterinherited
nonNulls → Iterable<T>

  Available on Iterable<T?>, provided by the NullableIterableExtensions extension

  The non-`null` elements of this iterable.
  no setter
runtimeType → Type
  A representation of the runtime type of the object.
  no setterinherited
single → E
  Checks that this iterable has only one element, and returns that element.
  no setterinherited
singleOrNull → T?

  Available on Iterable<T>, provided by the IterableExtensions extension

  The single element of this iterator, or `null`.
  no setter
toJSIterable → JSIterable<T>

  Available on Iterable<T>, provided by the IterableToJSIterable extension

  A JSIterable wrapper that proxies to the Dart iterable API.
  no setter
wait → Future<List<T>>

  Available on Iterable<Future<T>>, provided by the FutureIterable extension

  Waits for futures in parallel.
  no setter

## Methods

add(E value) → void
  Adds `value` at the end of the queue.
addAll(Iterable<E> iterable) → void
  Adds all elements of `iterable` at the end of the queue. The length of the queue is extended by the length of `iterable`.
addFirst(E value) → void
  Adds `value` at the beginning of the queue.
addLast(E value) → void
  Adds `value` at the end of the queue.
any(bool test(E element)) → bool
  Checks whether any element of this iterable satisfies `test`.
  inherited
asNameMap() → Map<String, T>

  Available on Iterable<T>, provided by the EnumByName extension

  Creates a map from the names of enum values to the values.
byName(String name) → T

  Available on Iterable<T>, provided by the EnumByName extension

  Finds the enum value in this list with name `name`.
cast<R>() → Queue<R>
  Provides a view of this queue as a queue of `R` instances, if necessary.
  override
clear() → void
  Removes all elements in the queue. The size of the queue becomes zero.
contains(Object? element) → bool
  Whether the collection contains an element equal to `element`.
  inherited
elementAt(int index) → E
  Returns the `index`th element.
  inherited
elementAtOrNull(int index) → T?

  Available on Iterable<T>, provided by the IterableExtensions extension

  The element at position `index` of this iterable, or `null`.
every(bool test(E element)) → bool
  Checks whether every element of this iterable satisfies `test`.
  inherited
expand<T>(Iterable<T> toElements(E element)) → Iterable<T>
  Expands each element of this Iterable into zero or more elements.
  inherited
firstWhere(bool test(E element), {E orElse()?}) → E
  The first element that satisfies the given predicate `test`.
  inherited
fold<T>(T initialValue, T combine(T previousValue, E element)) → T
  Reduces a collection to a single value by iteratively combining each element of the collection with an existing value
  inherited
followedBy(Iterable<E> other) → Iterable<E>
  Creates the lazy concatenation of this iterable and `other`.
  inherited
forEach(void action(E value)) → void
  Invokes `action` on each element of this iterable in iteration order.
  inherited
join([String separator = ""]) → String
  Converts each element to a String and concatenates the strings.
  inherited
lastWhere(bool test(E element), {E orElse()?}) → E
  The last element that satisfies the given predicate `test`.
  inherited
map<T>(T toElement(E e)) → Iterable<T>
  The current elements of this iterable modified by `toElement`.
  inherited
noSuchMethod(Invocation invocation) → dynamic
  Invoked when a nonexistent method or property is accessed.
  inherited
reduce(E combine(E value, E element)) → E
  Reduces a collection to a single value by iteratively combining elements of the collection using the provided function.
  inherited
remove(Object? value) → bool
  Removes a single instance of `value` from the queue.
removeFirst() → E
  Removes and returns the first element of this queue.
removeLast() → E
  Removes and returns the last element of the queue.
removeWhere(bool test(E element)) → void
  Removes all elements matched by `test` from the queue.
retainWhere(bool test(E element)) → void
  Removes all elements not matched by `test` from the queue.
singleWhere(bool test(E element), {E orElse()?}) → E
  The single element that satisfies `test`.
  inherited
skip(int count) → Iterable<E>
  Creates an Iterable that provides all but the first `count` elements.
  inherited
skipWhile(bool test(E element)) → Iterable<E>
  Creates an `Iterable` that skips leading elements while `test` is satisfied.
  inherited
take(int count) → Iterable<E>
  Creates a lazy iterable of the `count` first elements of this iterable.
  inherited
takeWhile(bool test(E element)) → Iterable<E>
  Creates a lazy iterable of the leading elements satisfying `test`.
  inherited
toList({bool growable = true}) → List<E>
  Creates a List containing the elements of this Iterable.
  inherited
toSet() → Set<E>
  Creates a Set containing the same elements as this iterable.
  inherited
toString() → String
  A string representation of this object.
  inherited
where(bool test(E element)) → Iterable<E>
  Creates a new lazy Iterable with all elements that satisfy the predicate `test`.
  inherited
whereType<T>() → Iterable<T>
  Creates a new lazy Iterable with all elements that have type `T`.
  inherited

## Operators

operator ==(Object other) → bool
  The equality operator.
  inherited

## Static Methods

castFrom<S, T>(Queue<S> source) → Queue<T>
  Adapts `source` to be a `Queue<T>`.
  override