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

Available extensions

Constructors

Queue.new(): 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

average → double: Available on Iterable<num>, provided by the IterableNumberExtension extension
The arithmetic mean of the elements of a non-empty iterable.
no setter
average → double: Available on Iterable<int>, provided by the IterableIntegerExtension extension
The arithmetic mean of the elements of a non-empty iterable.
no setter
first → E: The first element.
no setterinherited
firstOrNull → T?: Available on Iterable<T>, provided by the IterableExtension extension
The first element, or null if the iterable is empty.
no setter
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
flattened → Iterable<T>: Available on Iterable<Iterable<T>>, provided by the IterableIterableExtension extension
The sequential elements of each iterable in this iterable.
no setter
flattenedToList → List<T>: Available on Iterable<Iterable<T>>, provided by the IterableIterableExtension extension
The sequential elements of each iterable in this iterable.
no setter
flattenedToSet → Set<T>: Available on Iterable<Iterable<T>>, provided by the IterableIterableExtension extension
The unique sequential elements of each iterable in this iterable.
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
lastOrNull → T?: Available on Iterable<T>, provided by the IterableExtension extension
The last element, or null if the iterable is empty.
no setter
length → int: The number of elements in this Iterable.
no setterinherited
max → int: Available on Iterable<int>, provided by the IterableIntegerExtension extension
A maximal element of the iterable.
no setter
max → double: Available on Iterable<double>, provided by the IterableDoubleExtension extension
A maximal element of the iterable.
no setter
max → num: Available on Iterable<num>, provided by the IterableNumberExtension extension
A maximal element of the iterable.
no setter
max → T: Available on Iterable<T>, provided by the IterableComparableExtension extension
A maximal element of the iterable.
no setter
maxOrNull → double?: Available on Iterable<double>, provided by the IterableDoubleExtension extension
A maximal element of the iterable, or null if the iterable is empty.
no setter
maxOrNull → int?: Available on Iterable<int>, provided by the IterableIntegerExtension extension
A maximal element of the iterable, or null if the iterable is empty.
no setter
maxOrNull → T?: Available on Iterable<T>, provided by the IterableComparableExtension extension
A maximal element of the iterable, or null if the iterable is empty.
no setter
maxOrNull → num?: Available on Iterable<num>, provided by the IterableNumberExtension extension
A maximal element of the iterable, or null if the iterable is empty.
no setter
min → double: Available on Iterable<double>, provided by the IterableDoubleExtension extension
A minimal element of the iterable.
no setter
min → T: Available on Iterable<T>, provided by the IterableComparableExtension extension
A minimal element of the iterable.
no setter
min → int: Available on Iterable<int>, provided by the IterableIntegerExtension extension
A minimal element of the iterable.
no setter
min → num: Available on Iterable<num>, provided by the IterableNumberExtension extension
A minimal element of the iterable.
no setter
minOrNull → double?: Available on Iterable<double>, provided by the IterableDoubleExtension extension
A minimal element of the iterable, or null it the iterable is empty.
no setter
minOrNull → int?: Available on Iterable<int>, provided by the IterableIntegerExtension extension
A minimal element of the iterable, or null it the iterable is empty.
no setter
minOrNull → T?: Available on Iterable<T>, provided by the IterableComparableExtension extension
A minimal element of the iterable, or null it the iterable is empty.
no setter
minOrNull → num?: Available on Iterable<num>, provided by the IterableNumberExtension extension
A minimal element of the iterable, or null it the iterable is empty.
no setter
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 IterableExtension extension
The single element of the iterable, or null.
no setter
singleOrNull → T?: Available on Iterable<T>, provided by the IterableExtensions extension
The single element of this iterator, or null.
no setter
sum → int: Available on Iterable<int>, provided by the IterableIntegerExtension extension
The sum of the elements.
no setter
sum → num: Available on Iterable<num>, provided by the IterableNumberExtension extension
The sum of the elements.
no setter
sum → double: Available on Iterable<double>, provided by the IterableDoubleExtension extension
The sum of the elements.
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 indexth 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.
elementAtOrNull(int index) → T?: Available on Iterable<T>, provided by the IterableExtension extension
The indexth element, or null if there is no such element.
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
expandIndexed<R>(Iterable<R> expand(int index, T element)) → Iterable<R>: Available on Iterable<T>, provided by the IterableExtension extension
Expands each element and index to a number of elements in a new iterable.
firstWhere(bool test(E element), {E orElse()?}) → E: The first element that satisfies the given predicate test.
inherited
firstWhereIndexedOrNull(bool test(int index, T element)) → T?: Available on Iterable<T>, provided by the IterableExtension extension
The first element whose value and index satisfies test.
firstWhereOrNull(bool test(T element)) → T?: Available on Iterable<T>, provided by the IterableExtension extension
The first element satisfying test, or null if there are none.
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
foldIndexed<R>(R initialValue, R combine(int index, R previous, T element)) → R: Available on Iterable<T>, provided by the IterableExtension extension
Combine the elements with a value and the current index.
followedBy(Iterable<E> other) → Iterable<E>: Creates the lazy concatenation of this iterable and other.
inherited
forEach(void action(E element)) → void: Invokes action on each element of this iterable in iteration order.
inherited
forEachIndexed(void action(int index, T element)) → void: Available on Iterable<T>, provided by the IterableExtension extension
Takes an action for each element.
forEachIndexedWhile(bool action(int index, T element)) → void: Available on Iterable<T>, provided by the IterableExtension extension
Takes an action for each element and index as long as desired.
forEachWhile(bool action(T element)) → void: Available on Iterable<T>, provided by the IterableExtension extension
Takes an action for each element as long as desired.
groupFoldBy<K, G>(K keyOf(T element), G combine(G? previous, T element)) → Map<K, G>: Available on Iterable<T>, provided by the IterableExtension extension
Groups elements by keyOf then folds the elements in each group.
groupListsBy<K>(K keyOf(T element)) → Map<K, List<T>>: Available on Iterable<T>, provided by the IterableExtension extension
Groups elements into lists by keyOf.
groupSetsBy<K>(K keyOf(T element)) → Map<K, Set<T>>: Available on Iterable<T>, provided by the IterableExtension extension
Groups elements into sets by keyOf.
isSorted([Comparator<T>? compare]) → bool: Available on Iterable<T>, provided by the IterableComparableExtension extension
Whether the elements are sorted by the compare ordering.
isSorted(Comparator<T> compare) → bool: Available on Iterable<T>, provided by the IterableExtension extension
Whether the elements are sorted by the compare ordering.
isSortedBy<K extends Comparable<K>>(K keyOf(T element)) → bool: Available on Iterable<T>, provided by the IterableExtension extension
Whether the elements are sorted by their keyOf property.
isSortedByCompare<K>(K keyOf(T element), Comparator<K> compare) → bool: Available on Iterable<T>, provided by the IterableExtension extension
Whether the elements are compare-sorted by their keyOf property.
join([String separator = ""]) → String: Converts each element to a String and concatenates the strings.
inherited
lastBy<K>(K key(T)) → Map<K, T>: Available on Iterable<T>, provided by the IterableExtension extension
Associates the elements in this by the value returned by key.
lastWhere(bool test(E element), {E orElse()?}) → E: The last element that satisfies the given predicate test.
inherited
lastWhereIndexedOrNull(bool test(int index, T element)) → T?: Available on Iterable<T>, provided by the IterableExtension extension
The last element whose index and value satisfies test.
lastWhereOrNull(bool test(T element)) → T?: Available on Iterable<T>, provided by the IterableExtension extension
The last element satisfying test, or null if there are none.
map<T>(T toElement(E e)) → Iterable<T>: The current elements of this iterable modified by toElement.
inherited
mapIndexed<R>(R convert(int index, T element)) → Iterable<R>: Available on Iterable<T>, provided by the IterableExtension extension
Maps each element and its index to a new value.
none(bool test(T)) → bool: Available on Iterable<T>, provided by the IterableExtension extension
Whether no element satisfies test.
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
reduceIndexed(T combine(int index, T previous, T element)) → T: Available on Iterable<T>, provided by the IterableExtension extension
Combine the elements with each other and the current index.
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.
sample(int count, [Random? random]) → List<T>: Available on Iterable<T>, provided by the IterableExtension extension
Selects count elements at random from this iterable.
shuffled([Random? random]) → List<T>: Available on Iterable<T>, provided by the IterableExtension extension
Creates a shuffled list of the elements of the iterable.
singleWhere(bool test(E element), {E orElse()?}) → E: The single element that satisfies test.
inherited
singleWhereIndexedOrNull(bool test(int index, T element)) → T?: Available on Iterable<T>, provided by the IterableExtension extension
The single element satisfying test.
singleWhereOrNull(bool test(T element)) → T?: Available on Iterable<T>, provided by the IterableExtension extension
The single element satisfying test.
skip(int count) → Iterable<E>: Creates an Iterable that provides all but the first count elements.
inherited
skipWhile(bool test(E value)) → Iterable<E>: Creates an Iterable that skips leading elements while test is satisfied.
inherited
slices(int length) → Iterable<List<T>>: Available on Iterable<T>, provided by the IterableExtension extension
Contiguous slices of this with the given length.
sorted(Comparator<T> compare) → List<T>: Available on Iterable<T>, provided by the IterableExtension extension
Creates a sorted list of the elements of the iterable.
sorted([Comparator<T>? compare]) → List<T>: Available on Iterable<T>, provided by the IterableComparableExtension extension
Creates a sorted list of the elements of the iterable.
sortedBy<K extends Comparable<K>>(K keyOf(T element)) → List<T>: Available on Iterable<T>, provided by the IterableExtension extension
Creates a sorted list of the elements of the iterable.
sortedByCompare<K>(K keyOf(T element), Comparator<K> compare) → List<T>: Available on Iterable<T>, provided by the IterableExtension extension
Creates a sorted list of the elements of the iterable.
splitAfter(bool test(T element)) → Iterable<List<T>>: Available on Iterable<T>, provided by the IterableExtension extension
Splits the elements into chunks after some elements.
splitAfterIndexed(bool test(int index, T element)) → Iterable<List<T>>: Available on Iterable<T>, provided by the IterableExtension extension
Splits the elements into chunks after some elements and indices.
splitBefore(bool test(T element)) → Iterable<List<T>>: Available on Iterable<T>, provided by the IterableExtension extension
Splits the elements into chunks before some elements.
splitBeforeIndexed(bool test(int index, T element)) → Iterable<List<T>>: Available on Iterable<T>, provided by the IterableExtension extension
Splits the elements into chunks before some elements and indices.
splitBetween(bool test(T first, T second)) → Iterable<List<T>>: Available on Iterable<T>, provided by the IterableExtension extension
Splits the elements into chunks between some elements.
splitBetweenIndexed(bool test(int index, T first, T second)) → Iterable<List<T>>: Available on Iterable<T>, provided by the IterableExtension extension
Splits the elements into chunks between some elements and indices.
take(int count) → Iterable<E>: Creates a lazy iterable of the count first elements of this iterable.
inherited
takeWhile(bool test(E value)) → 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
whereIndexed(bool test(int index, T element)) → Iterable<T>: Available on Iterable<T>, provided by the IterableExtension extension
The elements whose value and index satisfies test.
whereNot(bool test(T element)) → Iterable<T>: Available on Iterable<T>, provided by the IterableExtension extension
The elements that do not satisfy test.
whereNotIndexed(bool test(int index, T element)) → Iterable<T>: Available on Iterable<T>, provided by the IterableExtension extension
The elements whose value and index do not satisfy test.
whereNotNull() → Iterable<T>: Available on Iterable<T?>, provided by the IterableNullableExtension extension
The non-null elements of this Iterable.
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