LongSparseArray

public class LongSparseArray
extends Object implements Cloneable

java.lang.Object
   ↳ androidx.collection.LongSparseArray<E>

SparseArray mapping longs to Objects. Unlike a normal array of Objects, there can be gaps in the indices. It is intended to be more memory efficient than using a HashMap to map Longs to Objects, both because it avoids auto-boxing keys and its data structure doesn't rely on an extra entry object for each mapping.

Note that this container keeps its mappings in an array data structure, using a binary search to find keys. The 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%.

To help with performance, the container includes an optimization when removing keys: instead of compacting its array immediately, it leaves the removed entry marked as deleted. The entry can then be re-used for the same key, or compacted later in a single garbage collection step of all removed entries. This garbage collection will need to be performed at any time the array needs to be grown or the the map size or entry values are retrieved.

It is possible to iterate over the items in this container using keyAt(int) and valueAt(int). Iterating over the keys using keyAt(int) with ascending values of the index will return the keys in ascending order, or the values corresponding to the keys in ascending order in the case of valueAt(int).

Summary

Public constructors

LongSparseArray()

Creates a new LongSparseArray containing no mappings.

LongSparseArray(int initialCapacity)

Creates a new LongSparseArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings.

Public methods

void append(long key, E value)

Puts a key/value pair into the array, optimizing for the case where the key is greater than all existing keys in the array.

void clear()

Removes all key-value mappings from this LongSparseArray.

LongSparseArray<E> clone()
boolean containsKey(long key)

Returns true if the specified key is mapped.

boolean containsValue(E value)

Returns true if the specified value is mapped from any key.

void delete(long key)

This method is deprecated. Alias for remove(long).

E get(long key)

Gets the Object mapped from the specified key, or null if no such mapping has been made.

E get(long key, E valueIfKeyNotFound)

Gets the Object mapped from the specified key, or the specified Object if no such mapping has been made.

int indexOfKey(long key)

Returns the index for which keyAt(int) would return the specified key, or a negative number if the specified key is not mapped.

int indexOfValue(E value)

Returns an index for which valueAt(int) would return the specified key, or a negative number if no keys map to the specified value.

boolean isEmpty()

Return true if size() is 0.

long keyAt(int index)

Given an index in the range 0...size()-1, returns the key from the indexth key-value mapping that this LongSparseArray stores.

void put(long key, E value)

Adds a mapping from the specified key to the specified value, replacing the previous mapping from the specified key if there was one.

void putAll(LongSparseArray<? extends E> other)

Copies all of the mappings from the other to this map.

E putIfAbsent(long key, E value)

Add a new value to the array map only if the key does not already have a value or it is mapped to null.

void remove(long key)

Removes the mapping from the specified key, if there was any.

boolean remove(long key, Object value)

Remove an existing key from the array map only if it is currently mapped to value.

void removeAt(int index)

Removes the mapping at the specified index.

E replace(long key, E value)

Replace the mapping for key only if it is already mapped to a value.

boolean replace(long key, E oldValue, E newValue)

Replace the mapping for key only if it is already mapped to a value.

void setValueAt(int index, E value)

Given an index in the range 0...size()-1, sets a new value for the indexth key-value mapping that this LongSparseArray stores.

int size()

Returns the number of key-value mappings that this LongSparseArray currently stores.

String toString()

This implementation composes a string by iterating over its mappings.

E valueAt(int index)

Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this LongSparseArray stores.

Inherited methods

Public constructors

LongSparseArray

public LongSparseArray ()

Creates a new LongSparseArray containing no mappings.

LongSparseArray

public LongSparseArray (int initialCapacity)

Creates a new LongSparseArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings. If you supply an initial capacity of 0, the sparse array will be initialized with a light-weight representation not requiring any additional array allocations.

Parameters
initialCapacity int

Public methods

append

public void append (long key, 
                E value)

Puts a key/value pair into the array, optimizing for the case where the key is greater than all existing keys in the array.

Parameters
key long

value E

clear

public void clear ()

Removes all key-value mappings from this LongSparseArray.

clone

public LongSparseArray<E> clone ()

Returns
LongSparseArray<E>

containsKey

public boolean containsKey (long key)

Returns true if the specified key is mapped.

Parameters
key long

Returns
boolean

containsValue

public boolean containsValue (E value)

Returns true if the specified value is mapped from any key.

Parameters
value E

Returns
boolean

delete

public void delete (long key)

This method is deprecated.
Alias for remove(long).

Parameters
key long

get

public E get (long key)

Gets the Object mapped from the specified key, or null if no such mapping has been made.

Parameters
key long

Returns
E

get

public E get (long key, 
                E valueIfKeyNotFound)

Gets the Object mapped from the specified key, or the specified Object if no such mapping has been made.

Parameters
key long

valueIfKeyNotFound E

Returns
E

indexOfKey

public int indexOfKey (long key)

Returns the index for which keyAt(int) would return the specified key, or a negative number if the specified key is not mapped.

Parameters
key long

Returns
int

indexOfValue

public int indexOfValue (E value)

Returns an index for which valueAt(int) would return the specified key, or a negative number if no keys map to the specified value. Beware that this is a linear search, unlike lookups by key, and that multiple keys can map to the same value and this will find only one of them.

Parameters
value E

Returns
int

isEmpty

public boolean isEmpty ()

Return true if size() is 0.

Returns
boolean true if size() is 0.

keyAt

public long keyAt (int index)

Given an index in the range 0...size()-1, returns the key from the indexth key-value mapping that this LongSparseArray stores.

The keys corresponding to indices in ascending order are guaranteed to be in ascending order, e.g., keyAt(0) will return the smallest key and keyAt(size()-1) will return the largest key.

Parameters
index int

Returns
long

put

public void put (long key, 
                E value)

Adds a mapping from the specified key to the specified value, replacing the previous mapping from the specified key if there was one.

Parameters
key long

value E

putAll

public void putAll (LongSparseArray<? extends E> other)

Copies all of the mappings from the other to this map. The effect of this call is equivalent to that of calling put(long, Object) on this map once for each mapping from key to value in other.

Parameters
other LongSparseArray

putIfAbsent

public E putIfAbsent (long key, 
                E value)

Add a new value to the array map only if the key does not already have a value or it is mapped to null.

Parameters
key long: The key under which to store the value.
value E: The value to store for the given key.
Returns
E Returns the value that was stored for the given key, or null if there was no such key.

remove

public void remove (long key)

Removes the mapping from the specified key, if there was any.

Parameters
key long

remove

public boolean remove (long key, 
                Object value)

Remove an existing key from the array map only if it is currently mapped to value.

Parameters
key long: The key of the mapping to remove.
value Object: The value expected to be mapped to the key.
Returns
boolean Returns true if the mapping was removed.

removeAt

public void removeAt (int index)

Removes the mapping at the specified index.

Parameters
index int

replace

public E replace (long key, 
                E value)

Replace the mapping for key only if it is already mapped to a value.

Parameters
key long: The key of the mapping to replace.
value E: The value to store for the given key.
Returns
E Returns the previous mapped value or null.

replace

public boolean replace (long key, 
                E oldValue, 
                E newValue)

Replace the mapping for key only if it is already mapped to a value.

Parameters
key long: The key of the mapping to replace.
oldValue E: The value expected to be mapped to the key.
newValue E: The value to store for the given key.
Returns
boolean Returns true if the value was replaced.

setValueAt

public void setValueAt (int index, 
                E value)

Given an index in the range 0...size()-1, sets a new value for the indexth key-value mapping that this LongSparseArray stores.

Parameters
index int

value E

size

public int size ()

Returns the number of key-value mappings that this LongSparseArray currently stores.

Returns
int

toString

public String toString ()

This implementation composes a string by iterating over its mappings. If this map contains itself as a value, the string "(this Map)" will appear in its place.

Returns
String

valueAt

public E valueAt (int index)

Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this LongSparseArray stores.

The values corresponding to indices in ascending order are guaranteed to be associated with keys in ascending order, e.g., valueAt(0) will return the value associated with the smallest key and valueAt(size()-1) will return the value associated with the largest key.

Parameters
index int

Returns
E