Set<E> class abstract interface

A collection of objects in which each object can occur only once.

That is, for each object of the element type, the object is either considered to be in the set, or to not be in the set.

Set implementations may consider some elements indistinguishable. These elements are treated as being the same for any operation on the set.

The default Set implementation, LinkedHashSet, considers objects indistinguishable if they are equal with regard to Object.== and Object.hashCode.

Iterating over elements of a set may be either unordered or ordered in some way. Examples:

A HashSet is unordered, which means that its iteration order is unspecified,
LinkedHashSet iterates in the insertion order of its elements, and
a sorted set like SplayTreeSet iterates the elements in sorted order.

It is generally not allowed to modify the set (add or remove elements) while an operation on the set is being performed, for example during a call to forEach or containsAll. Nor is it allowed to modify the set while iterating either the set itself or any Iterable that is backed by the set, such as the ones returned by methods like where and map.

It is generally not allowed to modify the equality of elements (and thus not their hashcode) while they are in the set. Some specialized subtypes may be more permissive, in which case they should document this behavior.

Implemented types

Iterable<E>

Implementers

Available extensions

Constructors

Set(): Creates an empty Set.
factory
Set.from(Iterable elements): Creates a Set that contains all elements.
factory
Set.identity(): Creates an empty identity Set.
factory
Set.of(Iterable<E> elements): Creates a Set from elements.
factory
Set.unmodifiable(Iterable<E> elements): Creates an unmodifiable Set 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>: An iterator that iterates over the elements of this set.
no setteroverride
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
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) → bool: Adds value to the set.
addAll(Iterable<E> elements) → void: Adds all elements to this set.
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>() → Set<R>: Provides a view of this set as a set of R instances.
override
clear() → void: Removes all elements from the set.
contains(Object? value) → bool: Whether value is in the set.
override
containsAll(Iterable<Object?> other) → bool: Whether this set contains all the elements of other.
difference(Set<Object?> other) → Set<E>: Creates a new set with the elements of this that are not in other.
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.
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 element)) → void: Invokes action on each element of this iterable in iteration order.
inherited
intersection(Set<Object?> other) → Set<E>: Creates a new set which is the intersection between this set and other.
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
lookup(Object? object) → E?: If an object equal to object is in the set, return it.
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 value from the set.
removeAll(Iterable<Object?> elements) → void: Removes each element of elements from this set.
removeWhere(bool test(E element)) → void: Removes all elements of this set that satisfy test.
retainAll(Iterable<Object?> elements) → void: Removes all elements of this set that are not elements in elements.
retainWhere(bool test(E element)) → void: Removes all elements of this set that fail to satisfy test.
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 value)) → 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 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 with the same elements and behavior as this Set.
override
toString() → String: A string representation of this object.
inherited
union(Set<E> other) → Set<E>: Creates a new set which contains all the elements of this set and other.
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>(Set<S> source, {Set<R> newSet<R>()?}) → Set<T>: Adapts source to be a Set<T>.
override