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
Constructors
- Map()
-
Creates a Map instance with the default implementation, LinkedHashMap.
factory - Map.from(Map other)
-
Creates a LinkedHashMap instance that contains all key-value pairs of
other.factory - 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.factory - Map.fromIterables(Iterable<K> keys, Iterable<V> values)
-
Creates a Map instance associating the given
keystovalues.factory - Map.identity()
-
Creates an identity map with the default implementation, LinkedHashMap.
factory - Map.unmodifiable(Map other)
-
Creates an unmodifiable hash based map containing the entries of
other.factory
Properties
- isEmpty → bool
-
Returns true if there is no key-value pair in the map.
read-only - isNotEmpty → bool
-
Returns true if there is at least one key-value pair in the map.
read-only - keys → Iterable<K>
-
The keys of
this.read-only - length → int
-
The number of key-value pairs in the map.
read-only - values → Iterable<V>
-
The values of
this.read-only - hashCode → int
-
The hash code for this object.
read-only, inherited - runtimeType → Type
-
A representation of the runtime type of the object.
read-only, inherited
Operators
-
operator [](
Object key) → V -
Returns the value for the given
keyor null ifkeyis not in the map. -
operator []=(
K key, V value) → void -
Associates the
keywith the givenvalue. -
operator ==(
other) → bool -
The equality operator.
inherited
Methods
-
addAll(
Map<K, V> other) → void -
Adds all key-value pairs of
otherto this map. -
clear(
) → void -
Removes all pairs from the map.
-
containsKey(
Object key) → bool -
Returns true if this map contains the given
key. -
containsValue(
Object value) → bool -
Returns true if this map contains the given
value. -
forEach(
void f(K key, V value)) → void -
Applies
fto each key-value pair of the map. -
putIfAbsent(
K key, V ifAbsent()) → V -
Look up the value of
key, or add a new value if it isn't there. -
remove(
Object key) → V -
Removes
keyand its associated value, if present, from the map. -
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a non-existent method or property is accessed.
inherited -
toString(
) → String -
Returns a string representation of this object.
inherited