SparseArrayCompat

public class SparseArrayCompat<E extends Object>


SparseArrays map integers 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 Integers 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 map size or entry values are retrieved.

It is possible to iterate over the items in this container using keyAt and valueAt. Iterating over the keys using keyAt 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.

Summary

Public constructors

<E extends Object> SparseArrayCompat(int initialCapacity)

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

Public methods

void
append(int key, @NonNull 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

Removes all key-value mappings from this SparseArray.

@NonNull SparseArrayCompat<@NonNull E>
boolean
containsKey(int key)

Returns true if the specified key is mapped.

boolean

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

void
delete(int key)

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

E
get(int key)

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

@NonNull E
get(int key, @NonNull E defaultValue)

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

final boolean

Return true if size is 0.

int
indexOfKey(int key)

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

int

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

boolean

Return true if size is 0.

int
keyAt(int index)

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

void
put(int key, @NonNull 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

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

E
putIfAbsent(int key, @NonNull 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(int key)

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

boolean
remove(int 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.

void
removeAtRange(int index, int size)

Remove a range of mappings as a batch.

E
replace(int key, @NonNull E value)

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

boolean
replace(int key, @NonNull E oldValue, @NonNull E newValue)

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

void
setValueAt(int index, @NonNull E value)

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

int

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

@NonNull String

Returns a string representation of the object.

@NonNull E
valueAt(int index)

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

Extension functions

final boolean
<T extends Object> SparseArrayKt.contains(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    int key
)

Returns true if the collection contains key.

final void
<T extends Object> SparseArrayKt.forEach(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    @NonNull Function2<@NonNull Integer, @NonNull value, Unit> action
)

Performs the given action for each key/value entry.

final @NonNull T
<T extends Object> SparseArrayKt.getOrDefault(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    int key,
    @NonNull T defaultValue
)

Return the value corresponding to key, or defaultValue when not present.

final @NonNull T
<T extends Object> SparseArrayKt.getOrElse(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    int key,
    @NonNull Function0<@NonNull T> defaultValue
)

Return the value corresponding to key, or from defaultValue when not present.

final int

Returns the number of key/value pairs in the collection.

final boolean
<T extends Object> SparseArrayKt.isNotEmpty(
    @NonNull SparseArrayCompat<@NonNull T> receiver
)

Return true when the collection contains elements.

final @NonNull IntIterator
<T extends Object> SparseArrayKt.keyIterator(
    @NonNull SparseArrayCompat<@NonNull T> receiver
)

Return an iterator over the collection's keys.

final @NonNull SparseArrayCompat<@NonNull T>
<T extends Object> SparseArrayKt.plus(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    @NonNull SparseArrayCompat<@NonNull T> other
)

Creates a new collection by adding or replacing entries from other.

final void
<T extends Object> SparseArrayKt.set(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    int key,
    @NonNull T value
)

Allows the use of the index operator for storing values in the collection.

final @NonNull Iterator<@NonNull T>
<T extends Object> SparseArrayKt.valueIterator(
    @NonNull SparseArrayCompat<@NonNull T> receiver
)

Return an iterator over the collection's values.

Public constructors

SparseArrayCompat

public <E extends Object> SparseArrayCompat(int initialCapacity)

Creates a new SparseArray 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
int initialCapacity

initial capacity of the array. The array will not require any additional memory allocation to store the specified number of mappings. If you supply an initialCapacity of 0, the sparse array will be initialized with a light-weight representation not requiring any additional array allocations. Default initialCapacity is 10.

Public methods

append

Added in 1.0.0
public void append(int key, @NonNull 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.

clear

Added in 1.0.0
public void clear()

Removes all key-value mappings from this SparseArray.

clone

Added in 1.0.0
public @NonNull SparseArrayCompat<@NonNull E> clone()

containsKey

Added in 1.0.0
public boolean containsKey(int key)

Returns true if the specified key is mapped.

containsValue

Added in 1.0.0
public boolean containsValue(@NonNull E value)

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

delete

Added in 1.0.0
Deprecated in 1.1.0
public void delete(int key)

get

Added in 1.0.0
public E get(int key)

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

get

Added in 1.0.0
public @NonNullget(int key, @NonNull E defaultValue)

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

getIsEmpty

Added in 1.3.0
public final boolean getIsEmpty()

Return true if size is 0.

Returns
boolean

true if size is 0.

indexOfKey

Added in 1.0.0
public int indexOfKey(int key)

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

Parameters
int key

the key to search for

Returns
int

the index for which keyAt would return the specified key, or a negative number if the specified key is not mapped

indexOfValue

Added in 1.0.0
public int indexOfValue(@NonNull E value)

Returns an index for which valueAt 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.

Note also that unlike most collections' indexOf methods, this method compares values using === rather than equals.

isEmpty

Added in 1.0.0
public boolean isEmpty()

Return true if size is 0.

Returns
boolean

true if size is 0.

keyAt

Added in 1.0.0
public int keyAt(int index)

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

put

Added in 1.0.0
public void put(int key, @NonNull 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.

putAll

Added in 1.0.0
public void putAll(@NonNull SparseArrayCompat<@NonNull 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 on this map once for each mapping from key to value in other.

putIfAbsent

Added in 1.1.0
public E putIfAbsent(int key, @NonNull 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
int key

The key under which to store the value.

@NonNull E value

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

Added in 1.0.0
public void remove(int key)

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

remove

Added in 1.1.0
public boolean remove(int key, Object value)

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

Parameters
int key

The key of the mapping to remove.

Object value

The value expected to be mapped to the key.

Returns
boolean

Returns true if the mapping was removed.

removeAt

Added in 1.0.0
public void removeAt(int index)

Removes the mapping at the specified index.

removeAtRange

Added in 1.0.0
public void removeAtRange(int index, int size)

Remove a range of mappings as a batch.

Parameters
int index

Index to begin at

int size

Number of mappings to remove

replace

Added in 1.1.0
public E replace(int key, @NonNull E value)

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

Parameters
int key

The key of the mapping to replace.

@NonNull E value

The value to store for the given key.

Returns
E

Returns the previous mapped value or null.

replace

Added in 1.1.0
public boolean replace(int key, @NonNull E oldValue, @NonNull E newValue)

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

Parameters
int key

The key of the mapping to replace.

@NonNull E oldValue

The value expected to be mapped to the key.

@NonNull E newValue

The value to store for the given key.

Returns
boolean

Returns true if the value was replaced.

setValueAt

Added in 1.0.0
public void setValueAt(int index, @NonNull E value)

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

size

Added in 1.0.0
public int size()

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

toString

public @NonNull String toString()

Returns a string representation of the object.

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.

valueAt

Added in 1.0.0
public @NonNullvalueAt(int index)

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

Extension functions

SparseArrayKt.contains

public final boolean <T extends Object> SparseArrayKt.contains(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    int key
)

Returns true if the collection contains key.

SparseArrayKt.forEach

public final void <T extends Object> SparseArrayKt.forEach(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    @NonNull Function2<@NonNull Integer, @NonNull value, Unit> action
)

Performs the given action for each key/value entry.

SparseArrayKt.getOrDefault

public final @NonNull T <T extends Object> SparseArrayKt.getOrDefault(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    int key,
    @NonNull T defaultValue
)

Return the value corresponding to key, or defaultValue when not present.

SparseArrayKt.getOrElse

public final @NonNull T <T extends Object> SparseArrayKt.getOrElse(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    int key,
    @NonNull Function0<@NonNull T> defaultValue
)

Return the value corresponding to key, or from defaultValue when not present.

SparseArrayKt.getSize

public final int SparseArrayKt.getSize(@NonNull SparseArrayCompat<@NonNull T> receiver)

Returns the number of key/value pairs in the collection.

SparseArrayKt.isNotEmpty

public final boolean <T extends Object> SparseArrayKt.isNotEmpty(
    @NonNull SparseArrayCompat<@NonNull T> receiver
)

Return true when the collection contains elements.

SparseArrayKt.keyIterator

public final @NonNull IntIterator <T extends Object> SparseArrayKt.keyIterator(
    @NonNull SparseArrayCompat<@NonNull T> receiver
)

Return an iterator over the collection's keys.

SparseArrayKt.plus

public final @NonNull SparseArrayCompat<@NonNull T> <T extends Object> SparseArrayKt.plus(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    @NonNull SparseArrayCompat<@NonNull T> other
)

Creates a new collection by adding or replacing entries from other.

SparseArrayKt.set

public final void <T extends Object> SparseArrayKt.set(
    @NonNull SparseArrayCompat<@NonNull T> receiver,
    int key,
    @NonNull T value
)

Allows the use of the index operator for storing values in the collection.

SparseArrayKt.valueIterator

public final @NonNull Iterator<@NonNull T> <T extends Object> SparseArrayKt.valueIterator(
    @NonNull SparseArrayCompat<@NonNull T> receiver
)

Return an iterator over the collection's values.