HashSet<E> class Null safety

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.

The set allows null as an element.

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

Constructors

HashSet({bool equals(E, E), int hashCode(E), bool isValidKey(dynamic)})
Create a hash set using the provided equals as equality. [...]
factory
HashSet.from(Iterable elements)
Create a hash set containing all elements. [...]
factory
HashSet.identity()
Creates an unordered identity-based set. [...]
factory
HashSet.of(Iterable<E> elements)
Create a hash set containing all elements. [...]
factory

Properties

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

Methods

add(E value) → bool
Adds value to the set. [...]
inherited
addAll(Iterable<E> elements) → void
Adds all elements to this Set. [...]
inherited
any(bool test(E element)) → bool
Checks whether any element of this iterable satisfies test. [...]
inherited
cast<R>() → Set<R>
Provides a view of this set as a set of R instances. [...]
inherited
clear() → void
Removes all elements in the set.
inherited
contains(Object? value) → bool
Returns true if value is in the set.
inherited
containsAll(Iterable<Object?> other) → bool
Returns whether this Set contains all the elements of other.
inherited
difference(Set<Object?> other) → Set<E>
Returns a new set with the elements of this that are not in other. [...]
inherited
elementAt(int index) → E
Returns the indexth element. [...]
inherited
every(bool test(E element)) → bool
Checks whether every element of this iterable satisfies test. [...]
inherited
expand<T>(Iterable<T> f(E element)) → Iterable<T>
Expands each element of this Iterable into zero or more elements. [...]
inherited
firstWhere(bool test(E element), {E orElse()}) → E
Returns 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>
Returns the lazy concatentation of this iterable and other. [...]
inherited
forEach(void f(E element)) → void
Applies the function f to each element of this collection in iteration order.
inherited
intersection(Set<Object?> other) → Set<E>
Returns a new set which is the intersection between this set and other. [...]
inherited
join([String separator = ""]) → String
Converts each element to a String and concatenates the strings. [...]
inherited
lastWhere(bool test(E element), {E orElse()}) → E
Returns 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. [...]
inherited
map<T>(T f(E e)) → Iterable<T>
Returns a new lazy Iterable with elements that are created by calling f on each element of this Iterable in iteration order. [...]
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent 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. Returns true if value was in the set. Returns false otherwise. The method has no effect if value value was not in the set.
inherited
removeAll(Iterable<Object?> elements) → void
Removes each element of elements from this set.
inherited
removeWhere(bool test(E element)) → void
Removes all elements of this set that satisfy test.
inherited
retainAll(Iterable<Object?> elements) → void
Removes all elements of this set that are not elements in elements. [...]
inherited
retainWhere(bool test(E element)) → void
Removes all elements of this set that fail to satisfy test.
inherited
singleWhere(bool test(E element), {E orElse()}) → E
Returns the single element that satisfies test. [...]
inherited
skip(int count) → Iterable<E>
Returns an Iterable that provides all but the first count elements. [...]
inherited
skipWhile(bool test(E value)) → Iterable<E>
Returns an Iterable that skips leading elements while test is satisfied. [...]
inherited
take(int count) → Iterable<E>
Returns a lazy iterable of the count first elements of this iterable. [...]
inherited
takeWhile(bool test(E value)) → Iterable<E>
Returns 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
Returns a string representation of this object.
inherited
union(Set<E> other) → Set<E>
Returns a new set which contains all the elements of this set and other. [...]
inherited
where(bool test(E element)) → Iterable<E>
Returns a new lazy Iterable with all elements that satisfy the predicate test. [...]
inherited
whereType<T>() → Iterable<T>
Returns a new lazy Iterable with all elements that have type T. [...]
inherited

Operators

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