class
Map<K, V>

An collection of key-value pairs, from which you retrieve a value using its associated key.

There is a finite number of keys in the map, and each key has exactly one value associated with it.

Maps, and their keys and values, can be iterated. The order of iteration is defined by the individual type of map. Examples:

  • The plain HashMap is unordered (no order is guaranteed),
  • the LinkedHashMap iterates in key insertion order,
  • and a sorted map like SplayTreeMap iterates the keys in sorted order.

It is generally not allowed to modify the map (add or remove keys) while an operation is being performed on the map, for example in functions called during a forEach or putIfAbsent call. Modifying the map while iterating the keys or values may also break the iteration.

Implemented by

Properties

Iterable<K> keys
read-only
The keys of [this].
Iterable<V> values
read-only
The values of [this].
int length
read-only
The number of key-value pairs in the map.
bool isEmpty
read-only
Returns true if there is no key-value pair in the map.
bool isNotEmpty
read-only
Returns true if there is at least one key-value pair in the map.

Constructors

Map()
Creates a Map instance with the default implementation, LinkedHashMap.
Map.from(Map other)
Creates a LinkedHashMap instance that contains all key-value pairs of other.
Map.unmodifiable(Map other)
Creates an unmodifiable hash based map containing the entries of other.
Map.identity()
Creates an identity map with the default implementation, LinkedHashMap.
Map.fromIterable(Iterable iterable, {K key(element), V value(element)})
Creates a Map instance in which the keys and values are computed from the iterable.
Map.fromIterables(Iterable<K> keys, Iterable<V> values)
Creates a Map instance associating the given keys to values.

Operators

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

Methods

containsValue(Object value) → bool
Returns true if this map contains the given value.
containsKey(Object key) → bool
Returns true if this map contains the given key.
putIfAbsent(K key, V ifAbsent()) → V
Look up the value of key, or add a new value if it isn't there.
addAll(Map<K,V> other) → void
Adds all key-value pairs of other to this map.
remove(Object key) → V
Removes key and its associated value, if present, from the map.
clear() → void
Removes all pairs from the map.
forEach(void f(K key, V value)) → void
Applies f to each key-value pair of the map.