ArrayMap

Kotlin |Java

open class ArrayMap<K : Any!, V : Any!> : SimpleArrayMap<K, V>, MutableMap<K, V>

kotlin.Any
↳	androidx.collection.SimpleArrayMap<K, V>
	↳	androidx.collection.ArrayMap

ArrayMap is a generic key->value mapping data structure that is designed to be more memory efficient than a traditional java.util.HashMap, this implementation is a version of the platform's android.util.ArrayMap that can be used on older versions of the platform. It keeps its mappings in an array data structure -- an integer array of hash codes for each item, and an Object array of the key/value pairs. This allows it to avoid having to create an extra object for every entry put in to the map, and it also tries to control the growth of the size of these arrays more aggressively (since growing them only requires copying the entries in the array, not rebuilding a hash map).

If you don't need the standard Java container APIs provided here (iterators etc), consider using SimpleArrayMap instead.

Note that this implementation is not intended to be appropriate for data structures that may contain large numbers of items. It is generally slower than a traditional HashMap, since lookups require a binary search and adds and removes require inserting and deleting entries in the array. For containers holding up to hundreds of items, the performance difference is not significant, less than 50%.

Because this container is intended to better balance memory use, unlike most other standard Java containers it will shrink its array as items are removed from it. Currently you have no control over this shrinking -- if you set a capacity and then remove an item, it may reduce the capacity to better match the current size. In the future an explicit call to set the capacity should turn off this aggressive shrinking behavior.

Summary

Public constructors
<init>()
<init>(capacity: Int) Create a new ArrayMap with a given initial capacity.
<init>(map: SimpleArrayMap<Any!, Any!>!) Create a new ArrayMap with the mappings from the given ArrayMap.

Public methods
open Boolean	containsAll(@NonNull collection: MutableCollection<*>) Determine if the array map contains all of the keys in the given collection.
open Unit	putAll(from: Map<out K, V>) Perform a #put(Object, Object) of all key/value pairs in map
open Boolean	removeAll(@NonNull collection: MutableCollection<*>) Remove all keys in the array map that exist in the given collection.
open Boolean	retainAll(@NonNull collection: MutableCollection<*>) Remove all keys in the array map that do not exist in the given collection.

Inherited functions

From class SimpleArrayMap Unit clear() Make the array map empty. All storage is released. Unit ensureCapacity(minimumCapacity: Int) Ensure the array map can hold at least minimumCapacity items. Boolean equals(other: Any?) This implementation returns false if the object is not a Map or SimpleArrayMap, or if the maps have different sizes. Otherwise, for each key in this map, values of both maps are compared. If the values for any key are not equal, the method returns false, otherwise it returns true. Int hashCode() Int indexOfKey(@Nullable key: Any?) Returns the index of a key in the set. Boolean isEmpty() Return true if the array map contains no items. K keyAt(index: Int) Return the key at the given index in the array. V? put(key: K, value: V) Add a new value to the array map. Unit putAll(@NonNull array: SimpleArrayMap<out K, out V>) Perform a put(Object, Object) of all key/value pairs in array V? putIfAbsent(key: K, value: V) Add a new value to the array map only if the key does not already have a value or it is mapped to null. V removeAt(index: Int) Remove the key/value mapping at the given index. V? replace(key: K, value: V) Replace the mapping for key only if it is already mapped to a value. Boolean replace(key: K, oldValue: V, newValue: V) Replace the mapping for key only if it is already mapped to a value. V setValueAt(index: Int, value: V) Set the value at a given index in the array. String toString() This implementation composes a string by iterating over its mappings. If this map contains itself as a key or a value, the string "(this Map)" will appear in its place. V valueAt(index: Int) Return the value at the given index in the array.

Properties
open MutableSet<MutableEntry<K, V>>	entries Return a java.util.Set for iterating over and interacting with all mappings in the array map.
open MutableSet<K>	keys Return a java.util.Set for iterating over and interacting with all keys in the array map.
open MutableCollection<V>	values Return a java.util.Collection for iterating over and interacting with all values in the array map.

Public constructors

<init>

ArrayMap()

<init>

ArrayMap(capacity: Int)

Create a new ArrayMap with a given initial capacity.

<init>

ArrayMap(map: SimpleArrayMap<Any!, Any!>!)

Create a new ArrayMap with the mappings from the given ArrayMap.

Public methods

containsAll

open fun containsAll(@NonNull collection: MutableCollection<*>): Boolean

Determine if the array map contains all of the keys in the given collection.

Parameters
collection	MutableCollection<*>: The collection whose contents are to be checked against.

Return
Boolean	Returns true if this array map contains a key for every entry in collection, else returns false.

putAll

open fun putAll(from: Map<out K, V>): Unit

Perform a #put(Object, Object) of all key/value pairs in map

Parameters
map	The map whose contents are to be retrieved.

removeAll

open fun removeAll(@NonNull collection: MutableCollection<*>): Boolean

Remove all keys in the array map that exist in the given collection.

Parameters
collection	MutableCollection<*>: The collection whose contents are to be used to remove keys.

Return
Boolean	Returns true if any keys were removed from the array map, else false.

retainAll

open fun retainAll(@NonNull collection: MutableCollection<*>): Boolean

Remove all keys in the array map that do not exist in the given collection.

Parameters
collection	MutableCollection<*>: The collection whose contents are to be used to determine which keys to keep.

Return
Boolean	Returns true if any keys were removed from the array map, else false.

Properties

entries

open val entries: MutableSet<MutableEntry<K, V>>

Return a java.util.Set for iterating over and interacting with all mappings in the array map.

Note: this is a very inefficient way to access the array contents, it requires generating a number of temporary objects.

Note:

the semantics of this Set are subtly different than that of a java.util.HashMap: most important, the Map.Entry object returned by its iterator is a single object that exists for the entire iterator, so you can not hold on to it after calling Iterator.next.

keys

open val keys: MutableSet<K>

Return a java.util.Set for iterating over and interacting with all keys in the array map.

Note: this is a fairly inefficient way to access the array contents, it requires generating a number of temporary objects.

values

open val values: MutableCollection<V>

Return a java.util.Collection for iterating over and interacting with all values in the array map.

Note: this is a fairly inefficient way to access the array contents, it requires generating a number of temporary objects.