Set<E> class

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 operator Object.==.

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.

Inheritance

Object
Iterable<E>
Set

Implementers

Constructors

Set() factory: Creates an empty Set. [...]
Set.from(Iterable elements) factory: Creates a Set that contains all elements. [...]
Set.identity() factory: Creates an empty identity Set. [...]
Set.of(Iterable<E> elements) factory: Creates a Set from elements. [...]
Set.unmodifiable(Iterable<E> elements) factory: Creates an unmodifiable Set from elements. [...]

Properties

first → E read-only, inherited: Returns the first element. [...]
hashCode → int read-only, inherited: The hash code for this object. [...]
isEmpty → bool read-only, inherited: Returns true if there are no elements in this collection. [...]
isNotEmpty → bool read-only, inherited: Returns true if there is at least one element in this collection. [...]
iterator → Iterator<E> read-only, override: An iterator that iterates over the elements of this set. [...]
last → E read-only, inherited: Returns the last element. [...]
length → int read-only, inherited: Returns the number of elements in this. [...]
runtimeType → Type read-only, inherited: A representation of the runtime type of the object.
single → E read-only, inherited: Checks that this iterable has only one element, and returns that element. [...]

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 inherited: Checks whether any element of this iterable satisfies test. [...]
cast<R>() → Set<R> override: Provides a view of this set as a set of R instances. [...]
clear() → void: Removes all elements from the set.
contains(Object? value) → bool override: Whether value is in the set.
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 inherited: Returns the indexth element. [...]
every(bool test(E element)) → bool inherited: Checks whether every element of this iterable satisfies test. [...]
expand<T>(Iterable<T> f(E element)) → Iterable<T> inherited: Expands each element of this Iterable into zero or more elements. [...]
firstWhere(bool test(E element), {E orElse()}) → E inherited: Returns the first element that satisfies the given predicate test. [...]
fold<T>(T initialValue, T combine(T previousValue, E element)) → T inherited: Reduces a collection to a single value by iteratively combining each element of the collection with an existing value [...]
followedBy(Iterable<E> other) → Iterable<E> inherited: Returns the lazy concatenation of this iterable and other. [...]
forEach(void f(E element)) → void inherited: Applies the function f to each element of this collection in iteration order.
intersection(Set<Object?> other) → Set<E>: Creates a new set which is the intersection between this set and other. [...]
join([String separator = ""]) → String inherited: Converts each element to a String and concatenates the strings. [...]
lastWhere(bool test(E element), {E orElse()}) → E inherited: Returns the last element that satisfies the given predicate test. [...]
lookup(Object? object) → E?: If an object equal to object is in the set, return it. [...]
map<T>(T f(E e)) → Iterable<T> inherited: Returns a new lazy Iterable with elements that are created by calling f on each element of this Iterable in iteration order. [...]
noSuchMethod(Invocation invocation) → dynamic inherited: Invoked when a non-existent method or property is accessed. [...]
reduce(E combine(E value, E element)) → E inherited: Reduces a collection to a single value by iteratively combining elements of the collection using the provided function. [...]
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 inherited: Returns the single element that satisfies test. [...]
skip(int count) → Iterable<E> inherited: Returns an Iterable that provides all but the first count elements. [...]
skipWhile(bool test(E value)) → Iterable<E> inherited: Returns an Iterable that skips leading elements while test is satisfied. [...]
take(int count) → Iterable<E> inherited: Returns a lazy iterable of the count first elements of this iterable. [...]
takeWhile(bool test(E value)) → Iterable<E> inherited: Returns a lazy iterable of the leading elements satisfying test. [...]
toList({bool growable = true}) → List<E> inherited: Creates a List containing the elements of this Iterable. [...]
toSet() → Set<E> override: Creates a Set with the same elements and behavior as this Set. [...]
toString() → String inherited: Returns a string representation of (some of) the elements of this. [...]
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> inherited: Returns a new lazy Iterable with all elements that satisfy the predicate test. [...]
whereType<T>() → Iterable<T> inherited: Returns a new lazy Iterable with all elements that have type T. [...]

Operators

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

Static Methods

castFrom<S, T>(Set<S> source, {Set<R> newSet()}) → Set<T> override: Adapts source to be a Set<T>. [...]

© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dart.dev/stable/2.13.0/dart-core/Set-class.html