MutableScatterMap

Artifact: androidx.collection:collection

Added in 1.4.0

Kotlin |Java

public final class MutableScatterMap<K extends Object, V extends Object> extends ScatterMap

java.lang.Object
↳	androidx.collection.ScatterMap
	↳	androidx.collection.MutableScatterMap

MutableScatterMap is a container with a Map-like interface based on a flat hash table implementation (the key/value mappings are not stored by nodes but directly into arrays). The underlying implementation is designed to avoid all allocations on insertion, removal, retrieval, and iteration. Allocations may still happen on insertion when the underlying storage needs to grow to accommodate newly added entries to the table. In addition, this implementation minimizes memory usage by avoiding the use of separate objects to hold key/value pairs.

This implementation makes no guarantee as to the order of the keys and values stored, nor does it make guarantees that the order remains constant over time.

This implementation is not thread-safe: if multiple threads access this container concurrently, and one or more threads modify the structure of the map (insertion or removal for instance), the calling code must provide the appropriate synchronization. Multiple threads are safe to read from this map concurrently if no write is happening.

Note: when a Map is absolutely necessary, you can use the method asMap to create a thin wrapper around a MutableScatterMap. Please refer to asMap for more details and caveats.

Note: when a MutableMap is absolutely necessary, you can use the method asMutableMap to create a thin wrapper around a MutableScatterMap. Please refer to asMutableMap for more details and caveats.

MutableScatterMap and SimpleArrayMap: like SimpleArrayMap, MutableScatterMap is designed to avoid the allocation of extra objects when inserting new entries in the map. However, the implementation of MutableScatterMap offers better performance characteristics compared to SimpleArrayMap and is thus generally preferable. If memory usage is a concern, SimpleArrayMap automatically shrinks its storage to avoid using more memory than necessary. You can also control memory usage with MutableScatterMap by manually calling MutableScatterMap.trim.

Note: For the JS target the implementation delegates to a regular map.

See also
`Map`

Summary

Public constructors
`<K extends Object, V extends Object> MutableScatterMap(int initialCapacity)` Creates a new `MutableScatterMap`

Public methods
`final @NonNull Map<@NonNull K, @NonNull V>`	`asMutableMap()` Wraps this `ScatterMap` with a `MutableMap` interface.
`final void`	`clear()` Removes all mappings from this map.
`final @NonNull V`	`compute( @NonNull K key, @NonNull Function2<@NonNull key, value, @NonNull V> computeBlock )` Retrieves a value for `key` and computes a new value based on the existing value (or `null` if the key is not in the map).
`final @NonNull V`	`getOrPut(@NonNull K key, @NonNull Function0<@NonNull V> defaultValue)` Returns the value to which the specified `key` is mapped, if the value is present in the map and not `null`.
`final void`	`minusAssign(@NonNull K key)` Removes the specified `key` and its associated value from the map.
`final void`	`minusAssign(@NonNull K[] keys)` Removes the specified `keys` and their associated value from the map.
`final void`	`minusAssign(@NonNull Iterable<@NonNull K> keys)` Removes the specified `keys` and their associated value from the map.
`final void`	`minusAssign(@NonNull ObjectList<@NonNull K> keys)` Removes the specified `keys` and their associated value from the map.
`final void`	`minusAssign(@NonNull ScatterSet<@NonNull K> keys)` Removes the specified `keys` and their associated value from the map.
`final void`	`minusAssign(@NonNull Sequence<@NonNull K> keys)` Removes the specified `keys` and their associated value from the map.
`final void`	`plusAssign(@NonNull Map<@NonNull K, @NonNull V> from)` Puts all the key/value mappings in the `from` map into this map.
`final void`	`plusAssign(@NonNull ScatterMap<@NonNull K, @NonNull V> from)` Puts all the key/value mappings in the `from` map into this map.
`final void`	`plusAssign(@NonNull Pair<@NonNull K, @NonNull V> pair)` Puts the key/value mapping from the `pair` in this map, using the first element as the key, and the second element as the value.
`final void`	`plusAssign(@NonNull Pair[] pairs)` Puts all the `pairs` into this map, using the first component of the pair as the key, and the second component as the value.
`final void`	`plusAssign(@NonNull Iterable<@NonNull Pair<@NonNull K, @NonNull V>> pairs)` Puts all the `pairs` into this map, using the first component of the pair as the key, and the second component as the value.
`final void`	`plusAssign(@NonNull Sequence<@NonNull Pair<@NonNull K, @NonNull V>> pairs)` Puts all the `pairs` into this map, using the first component of the pair as the key, and the second component as the value.
`final V`	`put(@NonNull K key, @NonNull V value)` Creates a new mapping from `key` to `value` in this map.
`final void`	`putAll(@NonNull Map<@NonNull K, @NonNull V> from)` Puts all the key/value mappings in the `from` map into this map.
`final void`	`putAll(@NonNull ScatterMap<@NonNull K, @NonNull V> from)` Puts all the key/value mappings in the `from` map into this map.
`final void`	`putAll(@NonNull Pair[] pairs)` Puts all the `pairs` into this map, using the first component of the pair as the key, and the second component as the value.
`final void`	`putAll(@NonNull Iterable<@NonNull Pair<@NonNull K, @NonNull V>> pairs)` Puts all the `pairs` into this map, using the first component of the pair as the key, and the second component as the value.
`final void`	`putAll(@NonNull Sequence<@NonNull Pair<@NonNull K, @NonNull V>> pairs)` Puts all the `pairs` into this map, using the first component of the pair as the key, and the second component as the value.
`final V`	`remove(@NonNull K key)` Removes the specified `key` and its associated value from the map.
`final boolean`	`remove(@NonNull K key, @NonNull V value)` Removes the specified `key` and its associated value from the map if the associated value equals `value`.
`final void`	`removeIf( @NonNull Function2<@NonNull K, @NonNull V, @NonNull Boolean> predicate )` Removes any mapping for which the specified `predicate` returns true.
`final void`	`set(@NonNull K key, @NonNull V value)` Creates a new mapping from `key` to `value` in this map.
`final int`	`trim()` Trims this `MutableScatterMap`'s storage so it is sized appropriately to hold the current mappings.

Inherited methods

From androidx.collection.ScatterMap

`final boolean`	`all(@NonNull Function2<@NonNull K, @NonNull V, @NonNull Boolean> predicate)` Returns true if all entries match the given `predicate`.
`final boolean`	`any()` Returns `true` if this map has at least one entry.
`final boolean`	`any(@NonNull Function2<@NonNull K, @NonNull V, @NonNull Boolean> predicate)` Returns true if at least one entry matches the given `predicate`.
`final @NonNull Map<@NonNull K, @NonNull V>`	`asMap()` Wraps this `ScatterMap` with a `Map` interface.
`final boolean`	`contains(@NonNull K key)` Returns true if the specified `key` is present in this hash map, false otherwise.
`final boolean`	`containsKey(@NonNull K key)` Returns true if the specified `key` is present in this hash map, false otherwise.
`final boolean`	`containsValue(@NonNull V value)` Returns true if the specified `value` is present in this hash map, false otherwise.
`final int`	`count()` Returns the number of entries in this map.
`final int`	`count(@NonNull Function2<@NonNull K, @NonNull V, @NonNull Boolean> predicate)` Returns the number of entries matching the given `predicate`.
`boolean`	`equals(Object other)` Compares the specified object `other` with this hash map for equality.
`final void`	`forEach(@NonNull Function2<@NonNull key, @NonNull value, Unit> block)` Iterates over every key/value pair stored in this map by invoking the specified `block` lambda.
`final void`	`forEachKey(@NonNull Function1<@NonNull key, Unit> block)` Iterates over every key stored in this map by invoking the specified `block` lambda.
`final void`	`forEachValue(@NonNull Function1<@NonNull value, Unit> block)` Iterates over every value stored in this map by invoking the specified `block` lambda.
`final V`	`get(@NonNull K key)` Returns the value corresponding to the given `key`, or `null` if such a key is not present in the map.
`final int`	`getCapacity()` Returns the number of key-value pairs that can be stored in this map without requiring internal storage reallocation.
`final @NonNull V`	`getOrDefault(@NonNull K key, @NonNull V defaultValue)` Returns the value to which the specified `key` is mapped, or `defaultValue` if this map contains no mapping for the key.
`final @NonNull V`	`getOrElse(@NonNull K key, @NonNull Function0<@NonNull V> defaultValue)` Returns the value for the given `key` if the value is present and not null.
`final int`	`getSize()` Returns the number of key-value pairs in this map.
`int`	`hashCode()` Returns the hash code value for this map.
`final boolean`	`isEmpty()` Indicates whether this map is empty.
`final boolean`	`isNotEmpty()` Returns `true` if this map is not empty.
`final @NonNull String`	`joinToString( @NonNull CharSequence separator, @NonNull CharSequence prefix, @NonNull CharSequence postfix, int limit, @NonNull CharSequence truncated, Function2<@NonNull key, @NonNull value, @NonNull CharSequence> transform )` Creates a String from the elements separated by `separator` and using `prefix` before and `postfix` after, if supplied.
`final boolean`	`none()` Returns `true` if this map has no entries.
`@NonNull String`	`toString()` Returns a string representation of this map.

Public constructors

MutableScatterMap

public <K extends Object, V extends Object> MutableScatterMap(int initialCapacity)

Creates a new MutableScatterMap

Parameters
`int initialCapacity`	The initial desired capacity for this container. The container will honor this value by guaranteeing its internal structures can hold that many entries without requiring any allocations. The initial capacity can be set to 0.

Public methods

asMutableMap

Added in 1.4.0

public final @NonNull Map<@NonNull K, @NonNull V> asMutableMap()

Wraps this ScatterMap with a MutableMap interface. The MutableMap is backed by the ScatterMap, so changes to the ScatterMap are reflected in the MutableMap and vice-versa. If the ScatterMap is modified while an iteration over the MutableMap is in progress (and vice- versa), the results of the iteration are undefined.

Note: while this method is useful to use this MutableScatterMap with APIs accepting MutableMap interfaces, it is less efficient to do so than to use MutableScatterMap's APIs directly. While the MutableMap implementation returned by this method tries to be as efficient as possible, the semantics of MutableMap may require the allocation of temporary objects for access and iteration.

clear

Added in 1.4.0

public final void clear()

Removes all mappings from this map.

compute

Added in 1.4.0

public final @NonNull V compute(
    @NonNull K key,
    @NonNull Function2<@NonNull key, value, @NonNull V> computeBlock
)

Retrieves a value for key and computes a new value based on the existing value (or null if the key is not in the map). The computed value is then stored in the map for the given key.

Returns
`@NonNull V`	value computed by `computeBlock`.

getOrPut

Added in 1.4.0

public final @NonNull V getOrPut(@NonNull K key, @NonNull Function0<@NonNull V> defaultValue)

Returns the value to which the specified key is mapped, if the value is present in the map and not null. Otherwise, calls defaultValue() and puts the result in the map associated with key.

minusAssign

Added in 1.4.0

public final void minusAssign(@NonNull K key)

Removes the specified key and its associated value from the map.

minusAssign

Added in 1.4.0

public final void minusAssign(@NonNull K[] keys)

Removes the specified keys and their associated value from the map.

minusAssign

public final void minusAssign(@NonNull Iterable<@NonNull K> keys)

Removes the specified keys and their associated value from the map.

minusAssign

Added in 1.4.0

public final void minusAssign(@NonNull ObjectList<@NonNull K> keys)

Removes the specified keys and their associated value from the map.

minusAssign

Added in 1.4.0

public final void minusAssign(@NonNull ScatterSet<@NonNull K> keys)

Removes the specified keys and their associated value from the map.

minusAssign

public final void minusAssign(@NonNull Sequence<@NonNull K> keys)

Removes the specified keys and their associated value from the map.

plusAssign

public final void plusAssign(@NonNull Map<@NonNull K, @NonNull V> from)

Puts all the key/value mappings in the from map into this map.

plusAssign

Added in 1.4.0

public final void plusAssign(@NonNull ScatterMap<@NonNull K, @NonNull V> from)

Puts all the key/value mappings in the from map into this map.

plusAssign

public final void plusAssign(@NonNull Pair<@NonNull K, @NonNull V> pair)

Puts the key/value mapping from the pair in this map, using the first element as the key, and the second element as the value.

plusAssign

public final void plusAssign(@NonNull Pair[] pairs)

Puts all the pairs into this map, using the first component of the pair as the key, and the second component as the value.

plusAssign

public final void plusAssign(@NonNull Iterable<@NonNull Pair<@NonNull K, @NonNull V>> pairs)

Puts all the pairs into this map, using the first component of the pair as the key, and the second component as the value.

plusAssign

public final void plusAssign(@NonNull Sequence<@NonNull Pair<@NonNull K, @NonNull V>> pairs)

Puts all the pairs into this map, using the first component of the pair as the key, and the second component as the value.

put

Added in 1.4.0

public final V put(@NonNull K key, @NonNull V value)

Creates a new mapping from key to value in this map. If key is already present in the map, the association is modified and the previously associated value is replaced with value. If key is not present, a new entry is added to the map, which may require to grow the underlying storage and cause allocations. Return the previous value associated with the key, or null if the key was not present in the map.

putAll

public final void putAll(@NonNull Map<@NonNull K, @NonNull V> from)

Puts all the key/value mappings in the from map into this map.

putAll

Added in 1.4.0

public final void putAll(@NonNull ScatterMap<@NonNull K, @NonNull V> from)

Puts all the key/value mappings in the from map into this map.

putAll

public final void putAll(@NonNull Pair[] pairs)

Puts all the pairs into this map, using the first component of the pair as the key, and the second component as the value.

putAll

public final void putAll(@NonNull Iterable<@NonNull Pair<@NonNull K, @NonNull V>> pairs)

Puts all the pairs into this map, using the first component of the pair as the key, and the second component as the value.

putAll

public final void putAll(@NonNull Sequence<@NonNull Pair<@NonNull K, @NonNull V>> pairs)

Puts all the pairs into this map, using the first component of the pair as the key, and the second component as the value.

remove

Added in 1.4.0

public final V remove(@NonNull K key)

Removes the specified key and its associated value from the map. If the key was present in the map, this function returns the value that was present before removal.

remove

Added in 1.4.0

public final boolean remove(@NonNull K key, @NonNull V value)

Removes the specified key and its associated value from the map if the associated value equals value. Returns whether the removal happened.

removeIf

Added in 1.4.0

public final void removeIf(
    @NonNull Function2<@NonNull K, @NonNull V, @NonNull Boolean> predicate
)

Removes any mapping for which the specified predicate returns true.

set

Added in 1.4.0

public final void set(@NonNull K key, @NonNull V value)

trim

Added in 1.4.0

public final int trim()

Trims this MutableScatterMap's storage so it is sized appropriately to hold the current mappings.

Returns the number of empty entries removed from this map's storage. Returns be 0 if no trimming is necessary or possible.