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
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. [...]
hashCodeint
read-only, inherited
The hash code for this object. [...]
isEmptybool
read-only, inherited
Returns true if there are no elements in this collection. [...]
isNotEmptybool
read-only, inherited
Returns true if there is at least one element in this collection. [...]
iteratorIterator<E>
read-only, override
An iterator that iterates over the elements of this set. [...]
last → E
read-only, inherited
Returns the last element. [...]
lengthint
read-only, inherited
Returns the number of elements in this. [...]
runtimeTypeType
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