MutableMap

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interface MutableMap<K, V> : Map<K, V>

A modifiable collection that holds pairs of objects (keys and values) and supports efficiently retrieving the value corresponding to each key. Map keys are unique; the map holds only one value for each key.

Parameters

K - the type of map keys. The map is invariant on its key type.

V - the type of map values. The mutable map is invariant on its value type.

Types

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MutableEntry

Represents a key/value pair held by a MutableMap.

interface MutableEntry<K, V> : Entry<K, V>

Properties

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entries

Returns a MutableSet of all key/value pairs in this map.

abstract val entries: MutableSet<MutableEntry<K, V>>
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keys

Returns a MutableSet of all keys in this map.

abstract val keys: MutableSet<K>
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values

Returns a MutableCollection of all values in this map. Note that this collection may contain duplicate values.

abstract val values: MutableCollection<V>

Functions

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clear

Removes all elements from this map.

abstract fun clear()
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put

Associates the specified value with the specified key in the map.

abstract fun put(key: K, value: V): V?
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putAll

Updates this map with key/value pairs from the specified map from.

abstract fun putAll(from: Map<out K, V>)
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remove

Removes the specified key and its corresponding value from this map.

abstract fun remove(key: K): V?

Removes the entry for the specified key only if it is mapped to the specified value.

open fun remove(key: K, value: V): Boolean

Extension Functions

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all

Returns true if all entries match the given predicate.

fun <K, V> Map<out K, V>.all(
    predicate: (Entry<K, V>) -> Boolean
): Boolean
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any

Returns true if map has at least one entry.

fun <K, V> Map<out K, V>.any(): Boolean

Returns true if at least one entry matches the given predicate.

fun <K, V> Map<out K, V>.any(
    predicate: (Entry<K, V>) -> Boolean
): Boolean
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asIterable

Creates an Iterable instance that wraps the original map returning its entries when being iterated.

fun <K, V> Map<out K, V>.asIterable(): Iterable<Entry<K, V>>
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asSequence

Creates a Sequence instance that wraps the original map returning its entries when being iterated.

fun <K, V> Map<out K, V>.asSequence(): Sequence<Entry<K, V>>
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contains

Checks if the map contains the given key.

operator fun <K, V> Map<out K, V>.contains(key: K): Boolean
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containsKey

Returns true if the map contains the specified key.

fun <K> Map<out K, *>.containsKey(key: K): Boolean
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containsValue

Returns true if the map maps one or more keys to the specified value.

fun <K, V> Map<K, V>.containsValue(value: V): Boolean
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count

Returns the number of entries in this map.

fun <K, V> Map<out K, V>.count(): Int

Returns the number of entries matching the given predicate.

fun <K, V> Map<out K, V>.count(
    predicate: (Entry<K, V>) -> Boolean
): Int
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filter

Returns a new map containing all key-value pairs matching the given predicate.

fun <K, V> Map<out K, V>.filter(
    predicate: (Entry<K, V>) -> Boolean
): Map<K, V>
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filterKeys

Returns a map containing all key-value pairs with keys matching the given predicate.

fun <K, V> Map<out K, V>.filterKeys(
    predicate: (K) -> Boolean
): Map<K, V>
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filterNot

Returns a new map containing all key-value pairs not matching the given predicate.

fun <K, V> Map<out K, V>.filterNot(
    predicate: (Entry<K, V>) -> Boolean
): Map<K, V>
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filterNotTo

Appends all entries not matching the given predicate into the given destination.

fun <K, V, M : MutableMap<in K, in V>> Map<out K, V>.filterNotTo(
    destination: M,
    predicate: (Entry<K, V>) -> Boolean
): M
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filterTo

Appends all entries matching the given predicate into the mutable map given as destination parameter.

fun <K, V, M : MutableMap<in K, in V>> Map<out K, V>.filterTo(
    destination: M,
    predicate: (Entry<K, V>) -> Boolean
): M
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filterValues

Returns a map containing all key-value pairs with values matching the given predicate.

fun <K, V> Map<out K, V>.filterValues(
    predicate: (V) -> Boolean
): Map<K, V>
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flatMap

Returns a single list of all elements yielded from results of transform function being invoked on each entry of original map.

fun <K, V, R> Map<out K, V>.flatMap(
    transform: (Entry<K, V>) -> Iterable<R>
): List<R>
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flatMapTo

Appends all elements yielded from results of transform function being invoked on each entry of original map, to the given destination.

fun <K, V, R, C : MutableCollection<in R>> Map<out K, V>.flatMapTo(
    destination: C,
    transform: (Entry<K, V>) -> Iterable<R>
): C
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forEach

Performs the given action on each entry.

fun <K, V> Map<out K, V>.forEach(
    action: (Entry<K, V>) -> Unit)
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get

Returns the value corresponding to the given key, or null if such a key is not present in the map.

operator fun <K, V> Map<out K, V>.get(key: K): V?
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getOrElse

Returns the value for the given key, or the result of the defaultValue function if there was no entry for the given key.

fun <K, V> Map<K, V>.getOrElse(
    key: K,
    defaultValue: () -> V
): V
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getOrPut

Returns the value for the given key. If the key is not found in the map, calls the defaultValue function, puts its result into the map under the given key and returns it.

fun <K, V> MutableMap<K, V>.getOrPut(
    key: K,
    defaultValue: () -> V
): V
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getValue

Returns the value of the property for the given object from this mutable map.

operator fun <V, V1 : V> MutableMap<in String, out V>.getValue(
    thisRef: Any?,
    property: KProperty<*>
): V1

Returns the value for the given key or throws an exception if there is no such key in the map.

fun <K, V> Map<K, V>.getValue(key: K): V
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ifEmpty

Returns this map if it's not empty or the result of calling defaultValue function if the map is empty.

fun <M, R> M.ifEmpty(
    defaultValue: () -> R
): R where M : Map<*, *>, M : R
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isNotEmpty

Returns true if this map is not empty.

fun <K, V> Map<out K, V>.isNotEmpty(): Boolean
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isNullOrEmpty

Returns true if this nullable map is either null or empty.

fun <K, V> Map<out K, V>?.isNullOrEmpty(): Boolean
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iterator

Returns a MutableIterator over the mutable entries in the MutableMap.

operator fun <K, V> MutableMap<K, V>.iterator(): MutableIterator<MutableEntry<K, V>>
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map

Returns a list containing the results of applying the given transform function to each entry in the original map.

fun <K, V, R> Map<out K, V>.map(
    transform: (Entry<K, V>) -> R
): List<R>
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mapKeys

Returns a new Map with entries having the keys obtained by applying the transform function to each entry in this Map and the values of this map.

fun <K, V, R> Map<out K, V>.mapKeys(
    transform: (Entry<K, V>) -> R
): Map<R, V>
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mapKeysTo

Populates the given destination map with entries having the keys obtained by applying the transform function to each entry in this Map and the values of this map.

fun <K, V, R, M : MutableMap<in R, in V>> Map<out K, V>.mapKeysTo(
    destination: M,
    transform: (Entry<K, V>) -> R
): M
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mapNotNull

Returns a list containing only the non-null results of applying the given transform function to each entry in the original map.

fun <K, V, R : Any> Map<out K, V>.mapNotNull(
    transform: (Entry<K, V>) -> R?
): List<R>
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mapNotNullTo

Applies the given transform function to each entry in the original map and appends only the non-null results to the given destination.

fun <K, V, R : Any, C : MutableCollection<in R>> Map<out K, V>.mapNotNullTo(
    destination: C,
    transform: (Entry<K, V>) -> R?
): C
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mapTo

Applies the given transform function to each entry of the original map and appends the results to the given destination.

fun <K, V, R, C : MutableCollection<in R>> Map<out K, V>.mapTo(
    destination: C,
    transform: (Entry<K, V>) -> R
): C
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mapValues

Returns a new map with entries having the keys of this map and the values obtained by applying the transform function to each entry in this Map.

fun <K, V, R> Map<out K, V>.mapValues(
    transform: (Entry<K, V>) -> R
): Map<K, R>
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mapValuesTo

Populates the given destination map with entries having the keys of this map and the values obtained by applying the transform function to each entry in this Map.

fun <K, V, R, M : MutableMap<in K, in R>> Map<out K, V>.mapValuesTo(
    destination: M,
    transform: (Entry<K, V>) -> R
): M
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maxBy

Returns the first entry yielding the largest value of the given function or null if there are no entries.

fun <K, V, R : Comparable<R>> Map<out K, V>.maxBy(
    selector: (Entry<K, V>) -> R
): Entry<K, V>?
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maxWith

Returns the first entry having the largest value according to the provided comparator or null if there are no entries.

fun <K, V> Map<out K, V>.maxWith(
    comparator: Comparator<in Entry<K, V>>
): Entry<K, V>?
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minBy

Returns the first entry yielding the smallest value of the given function or null if there are no entries.

fun <K, V, R : Comparable<R>> Map<out K, V>.minBy(
    selector: (Entry<K, V>) -> R
): Entry<K, V>?
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minus

Returns a map containing all entries of the original map except the entry with the given key.

operator fun <K, V> Map<out K, V>.minus(key: K): Map<K, V>

Returns a map containing all entries of the original map except those entries the keys of which are contained in the given keys collection.

operator fun <K, V> Map<out K, V>.minus(
    keys: Iterable<K>
): Map<K, V>

Returns a map containing all entries of the original map except those entries the keys of which are contained in the given keys array.

operator fun <K, V> Map<out K, V>.minus(
    keys: Array<out K>
): Map<K, V>

Returns a map containing all entries of the original map except those entries the keys of which are contained in the given keys sequence.

operator fun <K, V> Map<out K, V>.minus(
    keys: Sequence<K>
): Map<K, V>
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minusAssign

Removes the entry with the given key from this mutable map.

operator fun <K, V> MutableMap<K, V>.minusAssign(key: K)

Removes all entries the keys of which are contained in the given keys collection from this mutable map.

operator fun <K, V> MutableMap<K, V>.minusAssign(
    keys: Iterable<K>)

Removes all entries the keys of which are contained in the given keys array from this mutable map.

operator fun <K, V> MutableMap<K, V>.minusAssign(
    keys: Array<out K>)

Removes all entries from the keys of which are contained in the given keys sequence from this mutable map.

operator fun <K, V> MutableMap<K, V>.minusAssign(
    keys: Sequence<K>)
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minWith

Returns the first entry having the smallest value according to the provided comparator or null if there are no entries.

fun <K, V> Map<out K, V>.minWith(
    comparator: Comparator<in Entry<K, V>>
): Entry<K, V>?
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none

Returns true if the map has no entries.

fun <K, V> Map<out K, V>.none(): Boolean

Returns true if no entries match the given predicate.

fun <K, V> Map<out K, V>.none(
    predicate: (Entry<K, V>) -> Boolean
): Boolean
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onEach

Performs the given action on each entry and returns the map itself afterwards.

fun <K, V, M : Map<out K, V>> M.onEach(
    action: (Entry<K, V>) -> Unit
): M
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orEmpty

Returns the Map if its not null, or the empty Map otherwise.

fun <K, V> Map<K, V>?.orEmpty(): Map<K, V>
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plus

Creates a new read-only map by replacing or adding an entry to this map from a given key-value pair.

operator fun <K, V> Map<out K, V>.plus(
    pair: Pair<K, V>
): Map<K, V>

Creates a new read-only map by replacing or adding entries to this map from a given collection of key-value pairs.

operator fun <K, V> Map<out K, V>.plus(
    pairs: Iterable<Pair<K, V>>
): Map<K, V>

Creates a new read-only map by replacing or adding entries to this map from a given array of key-value pairs.

operator fun <K, V> Map<out K, V>.plus(
    pairs: Array<out Pair<K, V>>
): Map<K, V>

Creates a new read-only map by replacing or adding entries to this map from a given sequence of key-value pairs.

operator fun <K, V> Map<out K, V>.plus(
    pairs: Sequence<Pair<K, V>>
): Map<K, V>

Creates a new read-only map by replacing or adding entries to this map from another map.

operator fun <K, V> Map<out K, V>.plus(
    map: Map<out K, V>
): Map<K, V>
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plusAssign

Appends or replaces the given pair in this mutable map.

operator fun <K, V> MutableMap<in K, in V>.plusAssign(
    pair: Pair<K, V>)

Appends or replaces all pairs from the given collection of pairs in this mutable map.

operator fun <K, V> MutableMap<in K, in V>.plusAssign(
    pairs: Iterable<Pair<K, V>>)

Appends or replaces all pairs from the given array of pairs in this mutable map.

operator fun <K, V> MutableMap<in K, in V>.plusAssign(
    pairs: Array<out Pair<K, V>>)

Appends or replaces all pairs from the given sequence of pairs in this mutable map.

operator fun <K, V> MutableMap<in K, in V>.plusAssign(
    pairs: Sequence<Pair<K, V>>)

Appends or replaces all entries from the given map in this mutable map.

operator fun <K, V> MutableMap<in K, in V>.plusAssign(
    map: Map<K, V>)
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putAll

Puts all the given pairs into this MutableMap with the first component in the pair being the key and the second the value.

fun <K, V> MutableMap<in K, in V>.putAll(
    pairs: Array<out Pair<K, V>>)

Puts all the elements of the given collection into this MutableMap with the first component in the pair being the key and the second the value.

fun <K, V> MutableMap<in K, in V>.putAll(
    pairs: Iterable<Pair<K, V>>)

Puts all the elements of the given sequence into this MutableMap with the first component in the pair being the key and the second the value.

fun <K, V> MutableMap<in K, in V>.putAll(
    pairs: Sequence<Pair<K, V>>)

remove

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Removes the specified key and its corresponding value from this map.

fun <K, V> MutableMap<out K, V>.remove(key: K): V?
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Removes the entry for the specified key only if it is currently mapped to the specified value.

fun <K, V> MutableMap<out K, out V>.remove(
    key: K,
    value: V
): Boolean
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set

Allows to use the index operator for storing values in a mutable map.

operator fun <K, V> MutableMap<K, V>.set(key: K, value: V)
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setValue

Stores the value of the property for the given object in this mutable map.

operator fun <V> MutableMap<in String, in V>.setValue(
    thisRef: Any?,
    property: KProperty<*>,
    value: V)
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toList

Returns a List containing all key-value pairs.

fun <K, V> Map<out K, V>.toList(): List<Pair<K, V>>
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toMap

Returns a new read-only map containing all key-value pairs from the original map.

fun <K, V> Map<out K, V>.toMap(): Map<K, V>

Populates and returns the destination mutable map with key-value pairs from the given map.

fun <K, V, M : MutableMap<in K, in V>> Map<out K, V>.toMap(
    destination: M
): M
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toMutableMap

Returns a new mutable map containing all key-value pairs from the original map.

fun <K, V> Map<out K, V>.toMutableMap(): MutableMap<K, V>
JVM
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toProperties

Converts this Map to a Properties object.

fun Map<String, String>.toProperties(): Properties
JVM
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toSortedMap

Converts this Map to a SortedMap using the given comparator so that iteration order will be in the order defined by the comparator.

fun <K, V> Map<out K, V>.toSortedMap(
    comparator: Comparator<in K>
): SortedMap<K, V>
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withDefault

Returns a wrapper of this mutable map, having the implicit default value provided with the specified function defaultValue.

fun <K, V> MutableMap<K, V>.withDefault(
    defaultValue: (key: K) -> V
): MutableMap<K, V>

Returns a wrapper of this read-only map, having the implicit default value provided with the specified function defaultValue.

fun <K, V> Map<K, V>.withDefault(
    defaultValue: (key: K) -> V
): Map<K, V>

Inheritors

AbstractMutableMap

Provides a skeletal implementation of the MutableMap interface.

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abstract class AbstractMutableMap<K, V> : MutableMap<K, V>
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abstract class AbstractMutableMap<K, V> : 
    MutableMap<K, V>,
    AbstractMap<K, V>
JS
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abstract class AbstractMutableMap<K, V> : 
    AbstractMap<K, V>,
    MutableMap<K, V>

HashMap

Hash table based implementation of the MutableMap interface.

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class HashMap<K, V> : MutableMap<K, V>
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typealias HashMap<K, V> = HashMap<K, V>
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open class HashMap<K, V> : 
    AbstractMutableMap<K, V>,
    MutableMap<K, V>

LinkedHashMap

Hash table based implementation of the MutableMap interface, which additionally preserves the insertion order of entries during the iteration.

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class LinkedHashMap<K, V> : MutableMap<K, V>
JVM
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typealias LinkedHashMap<K, V> = LinkedHashMap<K, V>
JS
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open class LinkedHashMap<K, V> : 
    HashMap<K, V>,
    MutableMap<K, V>
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typealias LinkedHashMap<K, V> = HashMap<K, V>