1. Dart
  2. dart:collection
  3. HashMap<K, V> abstract class

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

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