HashSet<E> class

An unordered hash-table based Set implementation.

The elements of a HashSet must have consistent equality and hashCode implementations. This means that the equals operation must define a stable equivalence relation on the elements (reflexive, symmetric, transitive, and consistent over time), and that the hashCode must consistent with equality, so that the same for objects that are considered equal.

Most simple operations on HashSet are done in (potentially amortized) constant time: add, contains, remove, and length, provided the hash codes of objects are well distributed.

The iteration order of the set is not specified and depends on the hashcodes of the provided elements. However, the order is stable: multiple iterations over the same set produce the same order, as long as the set is not modified.

Implemented types

Set<E>

Constructors

HashSet({bool equals(E, E), int hashCode(E), bool isValidKey(dynamic)}) factory: Create a hash set using the provided equals as equality. [...]
HashSet.from(Iterable elements) factory: Create a hash set containing all elements. [...]
HashSet.identity() factory: Creates an unordered identity-based set. [...]
HashSet.of(Iterable<E> elements) factory: Create a hash set containing all 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: Provides 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 the iterable. [...]
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 inherited: Adds value to the set. [...]
addAll(Iterable<E> elements) → void inherited: 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> inherited: Provides a view of this set as a set of R instances. [...]
clear() → void inherited: Removes all elements from the set.
contains(Object? value) → bool inherited: Whether value is in the set.
containsAll(Iterable<Object?> other) → bool inherited: Whether this set contains all the elements of other.
difference(Set<Object?> other) → Set<E> inherited: 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> inherited: 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? inherited: 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 inherited: Removes value from the set. [...]
removeAll(Iterable<Object?> elements) → void inherited: Removes each element of elements from this set.
removeWhere(bool test(E element)) → void inherited: Removes all elements of this set that satisfy test.
retainAll(Iterable<Object?> elements) → void inherited: Removes all elements of this set that are not elements in elements. [...]
retainWhere(bool test(E element)) → void inherited: 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> inherited: Creates a Set with the same elements and behavior as this Set. [...]
toString() → String inherited: A string representation of this object. [...]
union(Set<E> other) → Set<E> inherited: 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. [...]

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