# HashSet<E> class

A custom implementation of a hash set that implements the `Set<E>` interface.

This `HashSet` stores unique elements and provides constant-time operations for insertion, removal, and lookup in the average case.

It uses open addressing with chaining to resolve hash collisions: each bucket is a list of values (`List<E>`) that share the same hash index.

When the load factor (size / capacity) exceeds 0.75, the internal bucket array is resized to maintain efficiency.

### ⚙️ Design Highlights:

- Uses `_buckets: List<List<E>?>` for collision handling
- On collision: appends to the list in the corresponding bucket
- Grows dynamically when usage exceeds load factor threshold

### 📦 Example Usage:

    final set = HashSet<String>();
    set.add('apple');
    set.add('banana');
    set.add('apple'); // Duplicate, ignored

    print(set.contains('banana')); // true
    print(set.length); // 2
    print(set); // {apple, banana}

Implemented types
  - Set<E>
Available extensions
  - EnumByName
  - FutureIterable
  - IterableComparableExtension
  - IterableDoubleExtension
  - IterableExtension
  - IterableExtension
  - IterableExtensions
  - IterableIntegerExtension
  - IterableIterableExtension
  - IterableNullableExtension
  - IterableNumberExtension
  - NullableIterableExtensions
  - SetUtils
  - SortByPublic
Annotations
  - @Generic(HashSet)

## Constructors

HashSet.new()
  A custom implementation of a hash set that implements the `Set<E>` interface.

## Properties

average → double

  Available on Iterable<num>, provided by the IterableNumberExtension extension

  The arithmetic mean of the elements of a non-empty iterable.
  no setter
average → double

  Available on Iterable<int>, provided by the IterableIntegerExtension extension

  The arithmetic mean of the elements of a non-empty iterable.
  no setter
first → E
  The first element.
  no setter override
firstOrNull → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  The first element, or `null` if the iterable is empty.
  no setter
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
flattened → Iterable<T>

  Available on Iterable<Iterable<T>>, provided by the IterableIterableExtension extension

  The sequential elements of each iterable in this iterable.
  no setter
flattenedToList → List<T>

  Available on Iterable<Iterable<T>>, provided by the IterableIterableExtension extension

  The sequential elements of each iterable in this iterable.
  no setter
flattenedToSet → Set<T>

  Available on Iterable<Iterable<T>>, provided by the IterableIterableExtension extension

  The unique sequential elements of each iterable in this iterable.
  no setter
hashCode → int
  The hash code for this object.
  no setter inherited
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 setter override
isNotEmpty → bool
  Whether this collection has at least one element.
  no setter override
iterator → Iterator<E>
  An iterator that iterates over the elements of this set.
  no setter override
last → E
  The last element.
  no setter override
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
lastOrNull → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  The last element, or `null` if the iterable is empty.
  no setter
length → int
  The number of elements in this Iterable.
  no setter override
max → int

  Available on Iterable<int>, provided by the IterableIntegerExtension extension

  A maximal element of the iterable.
  no setter
max → double

  Available on Iterable<double>, provided by the IterableDoubleExtension extension

  A maximal element of the iterable.
  no setter
max → num

  Available on Iterable<num>, provided by the IterableNumberExtension extension

  A maximal element of the iterable.
  no setter
max → T

  Available on Iterable<T>, provided by the IterableComparableExtension extension

  A maximal element of the iterable.
  no setter
maxOrNull → double?

  Available on Iterable<double>, provided by the IterableDoubleExtension extension

  A maximal element of the iterable, or `null` if the iterable is empty.
  no setter
maxOrNull → int?

  Available on Iterable<int>, provided by the IterableIntegerExtension extension

  A maximal element of the iterable, or `null` if the iterable is empty.
  no setter
maxOrNull → T?

  Available on Iterable<T>, provided by the IterableComparableExtension extension

  A maximal element of the iterable, or `null` if the iterable is empty.
  no setter
maxOrNull → num?

  Available on Iterable<num>, provided by the IterableNumberExtension extension

  A maximal element of the iterable, or `null` if the iterable is empty.
  no setter
min → double

  Available on Iterable<double>, provided by the IterableDoubleExtension extension

  A minimal element of the iterable.
  no setter
min → T

  Available on Iterable<T>, provided by the IterableComparableExtension extension

  A minimal element of the iterable.
  no setter
min → int

  Available on Iterable<int>, provided by the IterableIntegerExtension extension

  A minimal element of the iterable.
  no setter
min → num

  Available on Iterable<num>, provided by the IterableNumberExtension extension

  A minimal element of the iterable.
  no setter
minOrNull → double?

  Available on Iterable<double>, provided by the IterableDoubleExtension extension

  A minimal element of the iterable, or `null` it the iterable is empty.
  no setter
minOrNull → int?

  Available on Iterable<int>, provided by the IterableIntegerExtension extension

  A minimal element of the iterable, or `null` it the iterable is empty.
  no setter
minOrNull → T?

  Available on Iterable<T>, provided by the IterableComparableExtension extension

  A minimal element of the iterable, or `null` it the iterable is empty.
  no setter
minOrNull → num?

  Available on Iterable<num>, provided by the IterableNumberExtension extension

  A minimal element of the iterable, or `null` it the iterable is empty.
  no setter
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 setter inherited
single → E
  Checks that this iterable has only one element, and returns that element.
  no setter override
singleOrNull → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  The single element of the iterable, or `null`.
  no setter
singleOrNull → T?

  Available on Iterable<T>, provided by the IterableExtensions extension

  The single element of this iterator, or `null`.
  no setter
sum → int

  Available on Iterable<int>, provided by the IterableIntegerExtension extension

  The sum of the elements.
  no setter
sum → num

  Available on Iterable<num>, provided by the IterableNumberExtension extension

  The sum of the elements.
  no setter
sum → double

  Available on Iterable<double>, provided by the IterableDoubleExtension extension

  The sum of the elements.
  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 element) → bool
  Adds `value` to the set.
  override
addAll(Iterable<E> elements) → void
  Adds all `elements` to this set.
  override
all(ConditionTester<T> test) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Checks whether all elements of this iterable satisfy `test`.
any(bool test(E element)) → bool
  Checks whether any element of this iterable satisfies `test`.
  override
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.
  override
contains(Object? element) → bool
  Whether `value` is in the set.
  override
containsAll(Iterable<Object?> other) → bool
  Whether this set contains all the elements of `other`.
  override
difference(Set<Object?> other) → Set<E>
  Creates a new set with the elements of this that are not in `other`.
  override
elementAt(int index) → E
  Returns the `index`th element.
  override
elementAtOrNull(int index) → T?

  Available on Iterable<T>, provided by the IterableExtensions extension

  The element at position `index` of this iterable, or `null`.
elementAtOrNull(int index) → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  The `index`th element, or `null` if there is no such element.
every(bool test(E element)) → bool
  Checks whether every element of this iterable satisfies `test`.
  override
expand<T>(Iterable<T> toElements(E element)) → Iterable<T>
  Expands each element of this Iterable into zero or more elements.
  override
expandIndexed<R>(Iterable<R> expand(int index, T element)) → Iterable<R>

  Available on Iterable<T>, provided by the IterableExtension extension

  Expands each element and index to a number of elements in a new iterable.
filter(ConditionTester<T> test) → Iterable<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  Filters elements based on a predicate (alias for `where`).
filterWhere(ConditionTester<T> test) → Iterable<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  Filters elements based on a predicate.
find(ConditionTester<T> test) → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  Finds the first element that satisfies the given predicate.
findIndex(ConditionTester<T> test) → int

  Available on Iterable<T>, provided by the IterableExtension extension

  Finds the index of the first element that satisfies the given predicate.
firstWhere(bool test(E element), {E orElse()?}) → E
  The first element that satisfies the given predicate `test`.
  override
firstWhereIndexedOrNull(bool test(int index, T element)) → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  The first element whose value and index satisfies `test`.
firstWhereOrNull(ConditionTester<T> test) → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  Returns the first element that satisfies the predicate or `null` if none match.
firstWhereOrNull(bool test(T element)) → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  The first element satisfying `test`, or `null` if there are none.
flatMap<E>(Iterable<E> selector(T item)) → Iterable<E>

  Available on Iterable<T>, provided by the IterableExtension extension

  Flattens lists of items into a single iterable.
flatten<E>(E? selector(T item)) → Iterable<E>

  Available on Iterable<T>, provided by the IterableExtension extension

  Transforms each element of the iterable into zero or more elements of type `E` and flattens the results.
flattenIterable<E>(Iterable<E>? selector(T item)) → Iterable<E>

  Available on Iterable<T>, provided by the IterableExtension extension

  Transforms each element of the iterable into zero or more results of type `E`, and flattens the resulting collections into a single iterable.
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
  override
foldIndexed<R>(R initialValue, R combine(int index, R previous, T element)) → R

  Available on Iterable<T>, provided by the IterableExtension extension

  Combine the elements with a value and the current index.
followedBy(Iterable<E> other) → Iterable<E>
  Creates the lazy concatenation of this iterable and `other`.
  override
forEach(void action(E element)) → void
  Invokes `action` on each element of this iterable in iteration order.
  override
forEachIndexed(void action(int index, T element)) → void

  Available on Iterable<T>, provided by the IterableExtension extension

  Takes an action for each element.
forEachIndexedWhile(bool action(int index, T element)) → void

  Available on Iterable<T>, provided by the IterableExtension extension

  Takes an action for each element and index as long as desired.
forEachWhile(bool action(T element)) → void

  Available on Iterable<T>, provided by the IterableExtension extension

  Takes an action for each element as long as desired.
get([int index = 0]) → T

  Available on Iterable<T>, provided by the IterableExtension extension

  Returns the element at the specified index.
getFirst() → T

  Available on Iterable<T>, provided by the IterableExtension extension

  Returns the first element of the iterable.
getLast() → T

  Available on Iterable<T>, provided by the IterableExtension extension

  Returns the last element of the iterable.
group<K>(K keySelector(T item)) → Map<K, List<T>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Groups the elements of the iterable by a key returned from the `keySelector` function.
groupBy<K>(K keySelector(T item)) → Map<K, List<T>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Groups elements of this iterable into a Map using the given `keySelector`.
groupByAndMap<K, V>(K keySelector(T item), V valueSelector(T item)) → Map<K, List<V>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Groups elements of this iterable into a Map using `keySelector`, and applies `valueSelector` to each element before storing it.
groupFoldBy<K, G>(K keyOf(T element), G combine(G? previous, T element)) → Map<K, G>

  Available on Iterable<T>, provided by the IterableExtension extension

  Groups elements by `keyOf` then folds the elements in each group.
groupListsBy<K>(K keyOf(T element)) → Map<K, List<T>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Groups elements into lists by `keyOf`.
groupSetsBy<K>(K keyOf(T element)) → Map<K, Set<T>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Groups elements into sets by `keyOf`.
indexWhereOrNull(ConditionTester<T> test) → int?

  Available on Iterable<T>, provided by the IterableExtension extension

  Finds the index of an element that satisfies the predicate or returns `null` if not found.
intersection(Set<Object?> other) → Set<E>
  Creates a new set which is the intersection between this set and `other`.
  override
isLengthBetween(int min, int max) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Checks if length of double value is BETWEEN minLength to max.
isLengthEqualTo(int other) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Checks if length of double value is EQUAL to max.
isLengthEt(int max) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Short form for `isLengthEqualTo`
isLengthGreaterThan(int max) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Checks if length of double value is GREATER than max.
isLengthGreaterThanOrEqualTo(int max) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Checks if length of double value is GREATER OR EQUAL to max.
isLengthGt(int max) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Short form for `isLengthGreaterThan`
isLengthGtEt(int max) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Short form for `isLengthGreaterThanOrEqualTo`
isLengthLessThan(int max) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Checks if length of double value is LESS than max.
isLengthLessThanOrEqualTo(int max) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Checks if length of double value is LESS OR EQUAL to max.
isLengthLt(int max) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Short form for `isLengthLessThan`
isLengthLtEt(int max) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Short form for `isLengthLessThanOrEqualTo`
isSorted(Comparator<T> compare) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Whether the elements are sorted by the `compare` ordering.
isSorted([Comparator<T>? compare]) → bool

  Available on Iterable<T>, provided by the IterableComparableExtension extension

  Whether the elements are sorted by the `compare` ordering.
isSortedBy<K extends Comparable<K>>(K keyOf(T element)) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Whether the elements are sorted by their `keyOf` property.
isSortedByCompare<K>(K keyOf(T element), Comparator<K> compare) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Whether the elements are `compare`-sorted by their `keyOf` property.
isSubsetOf(Set<Object?> other) → bool

  Available on Set<Object?>, provided by the SetUtils extension

  Utility extension methods for working with sets in Dart.
isSupersetOf(Set<Object?> other) → bool

  Available on Set<Object?>, provided by the SetUtils extension

  Utility extension methods for working with sets in Dart.
join([String separator = ""]) → String
  Converts each element to a String and concatenates the strings.
  override
lastBy<K>(K key(T)) → Map<K, T>

  Available on Iterable<T>, provided by the IterableExtension extension

  Associates the elements in `this` by the value returned by `key`.
lastWhere(bool test(E element), {E orElse()?}) → E
  The last element that satisfies the given predicate `test`.
  override
lastWhereIndexedOrNull(bool test(int index, T element)) → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  The last element whose index and value satisfies `test`.
lastWhereOrNull(bool test(T element)) → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  The last element satisfying `test`, or `null` if there are none.
lastWhereOrNull(ConditionTester<T> test) → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  Returns the last element that satisfies the predicate or `null` if none match.
lookup(Object? element) → E?
  If an object equal to `object` is in the set, return it.
  override
map<T>(T toElement(E e)) → Iterable<T>
  The current elements of this iterable modified by `toElement`.
  override
mapIndexed<R>(R convert(int index, T element)) → Iterable<R>

  Available on Iterable<T>, provided by the IterableExtension extension

  Maps each element and its index to a new value.
none(ConditionTester<T> test) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Checks if no element matches the predicate.
none(bool test(T)) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Whether no element satisfies `test`.
noneMatch(ConditionTester<T> test) → bool

  Available on Iterable<T>, provided by the IterableExtension extension

  Checks if none of the elements match a condition using noneMatch.
noSuchMethod(Invocation invocation) → dynamic
  Invoked when a nonexistent method or property is accessed.
  inherited
process(dynamic action(T item)) → void

  Available on Iterable<T>, provided by the IterableExtension extension

  Processes each element of the iterable using the provided `action` function.
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.
  override
reduceIndexed(T combine(int index, T previous, T element)) → T

  Available on Iterable<T>, provided by the IterableExtension extension

  Combine the elements with each other and the current index.
remove(Object? value) → bool
  Removes `value` from the set.
  override
removeAll(Iterable<Object?> elements) → void
  Removes each element of `elements` from this set.
  override
removeWhere(bool test(E element)) → void
  Removes all elements of this set that satisfy `test`.
  override
retainAll(Iterable<Object?> elements) → void
  Removes all elements of this set that are not elements in `elements`.
  override
retainWhere(bool test(E element)) → void
  Removes all elements of this set that fail to satisfy `test`.
  override
sample(int count, [Random? random]) → List<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  Selects `count` elements at random from this iterable.
shuffled([Random? random]) → List<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  Creates a shuffled list of the elements of the iterable.
singleWhere(bool test(E element), {E orElse()?}) → E
  The single element that satisfies `test`.
  override
singleWhereIndexedOrNull(bool test(int index, T element)) → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  The single element satisfying `test`.
singleWhereOrNull(bool test(T element)) → T?

  Available on Iterable<T>, provided by the IterableExtension extension

  The single element satisfying `test`.
skip(int count) → Iterable<E>
  Creates an Iterable that provides all but the first `count` elements.
  override
skipWhile(bool test(E value)) → Iterable<E>
  Creates an `Iterable` that skips leading elements while `test` is satisfied.
  override
slices(int length) → Iterable<List<T>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Contiguous slices of `this` with the given `length`.
sorted(Comparator<T> compare) → List<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  Creates a sorted list of the elements of the iterable.
sorted([Comparator<T>? compare]) → List<T>

  Available on Iterable<T>, provided by the IterableComparableExtension extension

  Creates a sorted list of the elements of the iterable.
sortedBy<K extends Comparable<K>>(K keyOf(T element)) → List<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  Creates a sorted list of the elements of the iterable.
sortedByCompare<K>(K keyOf(T element), Comparator<K> compare) → List<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  Creates a sorted list of the elements of the iterable.
sortedByPublicFirst() → List<T>

  Available on Iterable<T>, provided by the SortByPublic extension

  Sorts declarations with public visibility before private ones.
sortedByPublicFirstThenSyntheticLast() → List<T>

  Available on Iterable<T>, provided by the SortByPublic extension

  Sorts declarations with public visibility first and synthetic declarations last.
splitAfter(bool test(T element)) → Iterable<List<T>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Splits the elements into chunks after some elements.
splitAfterIndexed(bool test(int index, T element)) → Iterable<List<T>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Splits the elements into chunks after some elements and indices.
splitBefore(bool test(T element)) → Iterable<List<T>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Splits the elements into chunks before some elements.
splitBeforeIndexed(bool test(int index, T element)) → Iterable<List<T>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Splits the elements into chunks before some elements and indices.
splitBetween(bool test(T first, T second)) → Iterable<List<T>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Splits the elements into chunks between some elements.
splitBetweenIndexed(bool test(int index, T first, T second)) → Iterable<List<T>>

  Available on Iterable<T>, provided by the IterableExtension extension

  Splits the elements into chunks between some elements and indices.
stream() → GenericStream<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  Converts the iterable to a stream.
take(int count) → Iterable<E>
  Creates a lazy iterable of the `count` first elements of this iterable.
  override
takeWhile(bool test(E value)) → Iterable<E>
  Creates a lazy iterable of the leading elements satisfying `test`.
  override
toList({bool growable = true}) → List<E>
  Creates a List containing the elements of this Iterable.
  override
toMap<K, V>(K keySelector(T item), V valueSelector(T item)) → Map<K, V>

  Available on Iterable<T>, provided by the IterableExtension extension

  Maps the iterable to a new iterable using the provided `mapper` function.
toSet() → Set<E>
  Creates a Set with the same elements and behavior as this `Set`.
  override
toString() → String
  A string representation of this object.
  override
union(Set<E> other) → Set<E>
  Creates a new set which contains all the elements of this set and `other`.
  override
where(bool test(E element)) → Iterable<E>
  Creates a new lazy Iterable with all elements that satisfy the predicate `test`.
  override
whereIndexed(bool test(int index, T element)) → Iterable<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  The elements whose value and index satisfies `test`.
whereNot(bool test(T element)) → Iterable<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  The elements that do not satisfy `test`.
whereNotIndexed(bool test(int index, T element)) → Iterable<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  The elements whose value and index do not satisfy `test`.
whereNotNull() → Iterable<T>

  Available on Iterable<T?>, provided by the IterableNullableExtension extension

  The non-`null` elements of this `Iterable`.
whereOrNull(ConditionTester<T> test) → Iterable<T>?

  Available on Iterable<T>, provided by the IterableExtension extension

  Returns an iterable with elements that match a condition, or `null` if none match.
whereType<U>() → Iterable<T>

  Available on Iterable<T>, provided by the IterableExtension extension

  Filters elements of a specific type `T`.
whereType<T>() → Iterable<T>
  Creates a new lazy Iterable with all elements that have type `T`.
  override

## Operators

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