description

# HashMap<K, V> class

A hash-table based implementation of Map.

The keys of a `HashMap` must have consistent Object.== and Object.hashCode implementations. This means that the `==` operator must define a stable equivalence relation on the keys (reflexive, symmetric, transitive, and consistent over time), and that `hashCode` must be the same for objects that are considered equal by `==`.

The map allows `null` as a key.

Iterating the map's keys, values or entries (through forEach) may happen in any order. The iteration order only changes when the map is modified. Values are iterated in the same order as their associated keys, so iterating the keys and values in parallel will give matching key and value pairs.

Implemented types
  - Map<K, V>

## Constructors

HashMap({bool equals(K key1, K key2), int hashCode(K key), bool isValidKey(dynamic potentialKey) })
  Creates an unordered hash-table based Map. [...]
  factory
HashMap.from(Map other)
  Creates a HashMap that contains all key/value pairs of `other`. [...]
  factory
HashMap.fromEntries(Iterable<MapEntry<K, V>> entries)
  Creates a HashMap containing the entries of `entries`. [...]
  factory
HashMap.fromIterable(Iterable iterable, { K key(dynamic element), V value(dynamic element) })
  Creates a HashMap where the keys and values are computed from the `iterable`. [...]
  factory
HashMap.fromIterables(Iterable<K> keys, Iterable<V> values)
  Creates a HashMap associating the given `keys` to `values`. [...]
  factory
HashMap.identity()
  Creates an unordered identity-based map. [...]
  factory
HashMap.of(Map<K, V> other)
  Creates a HashMap that contains all key/value pairs of `other`.
  factory

## Properties

entries → Iterable<MapEntry<K, V>>
  The map entries of this.
  read-only, inherited
hashCode → int
  The hash code for this object. [...]
  read-only, inherited
isEmpty → bool
  Returns true if there is no key/value pair in the map.
  read-only, inherited
isNotEmpty → bool
  Returns true if there is at least one key/value pair in the map.
  read-only, inherited
keys → Iterable<K>
  The keys of this. [...]
  read-only, inherited
length → int
  The number of key/value pairs in the map.
  read-only, inherited
runtimeType → Type
  A representation of the runtime type of the object.
  read-only, inherited
values → Iterable<V>
  The values of this. [...]
  read-only, inherited

## Methods

addAll(Map<K, V> other) → void
  Adds all key/value pairs of `other` to this map. [...]
  inherited
addEntries(Iterable<MapEntry<K, V>> newEntries) → void
  Adds all key/value pairs of `newEntries` to this map. [...]
  inherited
cast<RK, RV>() → Map<RK, RV>
  Provides a view of this map as having `RK` keys and `RV` instances, if necessary. [...]
  inherited
clear() → void
  Removes all pairs from the map. [...]
  inherited
containsKey(Object key) → bool
  Returns true if this map contains the given `key`. [...]
  inherited
containsValue(Object value) → bool
  Returns true if this map contains the given `value`. [...]
  inherited
forEach(void f(K key, V value)) → void
  Applies `f` to each key/value pair of the map. [...]
  inherited
map<K2, V2>(MapEntry<K2, V2> f(K key, V value)) → Map<K2, V2>
  Returns a new map where all entries of this map are transformed by the given `f` function.
  inherited
noSuchMethod(Invocation invocation) → dynamic
  Invoked when a non-existent method or property is accessed. [...]
  inherited
putIfAbsent(K key, V ifAbsent()) → V
  Look up the value of `key`, or add a new value if it isn't there. [...]
  inherited
remove(Object key) → V
  Removes `key` and its associated value, if present, from the map. [...]
  inherited
removeWhere(bool predicate(K key, V value)) → void
  Removes all entries of this map that satisfy the given `predicate`.
  inherited
toString() → String
  Returns a string representation of this object.
  inherited
update(K key, V update(V value), { V ifAbsent() }) → V
  Updates the value for the provided `key`. [...]
  inherited
updateAll(V update(K key, V value)) → void
  Updates all values. [...]
  inherited

## Operators

operator ==(dynamic other) → bool
  The equality operator. [...]
  inherited
operator [](Object key) → V
  Returns the value for the given `key` or null if `key` is not in the map. [...]
  inherited
operator []=(K key, V value) → void
  Associates the `key` with the given `value`. [...]
  inherited