Added in API level 1

Summary: Ctors | Methods | Inherited Methods

SparseArray

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Kotlin |Java

public class SparseArray
extends Object implements Cloneable

java.lang.Object
↳	android.util.SparseArray<E>

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SparseArray maps integers to Objects and, unlike a normal array of Objects, its indices can contain gaps. SparseArray is intended to be more memory-efficient than a HashMap, 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 HashMap because 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 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 of all removed entries. This garbage collection must be performed whenever the array needs to be grown, or when 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 returns the keys in ascending order. In the case of valueAt(int), the values corresponding to the keys are returned in ascending order.

Summary

Public constructors
SparseArray() Creates a new SparseArray containing no mappings.
SparseArray(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, 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 SparseArray.
SparseArray<E>	clone() Creates and returns a copy of this object.
boolean	contains(int key) Returns true if the key exists in the array.
boolean	contentEquals(SparseArray<?> other) Compares the contents of this SparseArray to the specified SparseArray.
int	contentHashCode() Returns a hash code value for the contents of this SparseArray, combining the Objects#hashCode(Object) result of all its keys and values.
void	delete(int key) Removes the mapping from the specified key, if there was any.
E	get(int key) Gets the Object mapped from the specified key, or null if no such mapping has been made.
E	get(int key, E valueIfKeyNotFound) Gets the Object mapped from the specified key, or the specified Object if no such mapping has been made.
int	indexOfKey(int 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 value, or a negative number if no keys map to the specified value.
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, 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	remove(int key) Alias for delete(int).
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.
void	set(int key, E value) Alias for put(int, java.lang.Object) to support Kotlin [index]= operator.
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 SparseArray stores.
int	size() Returns the number of key-value mappings that this SparseArray currently stores.
String	toString() Returns a string representation of the object. 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 SparseArray stores.

Inherited methods

From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Public constructors

SparseArray

Added in API level 1

public SparseArray ()

Creates a new SparseArray containing no mappings.

SparseArray

Added in API level 1

public SparseArray (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
initialCapacity	int

Public methods

append

Added in API level 1

public void append (int 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	int
value	E

clear

Added in API level 1

public void clear ()

Removes all key-value mappings from this SparseArray.

clone

Added in API level 1

public SparseArray<E> clone ()

Creates and returns a copy of this object. The precise meaning of "copy" may depend on the class of the object. The general intent is that, for any object x, the expression:

 x.clone() != x

will be true, and that the expression:

 x.clone().getClass() == x.getClass()

will be true, but these are not absolute requirements. While it is typically the case that:

 x.clone().equals(x)

will be true, this is not an absolute requirement.

By convention, the returned object should be obtained by calling super.clone. If a class and all of its superclasses (except Object) obey this convention, it will be the case that x.clone().getClass() == x.getClass().

By convention, the object returned by this method should be independent of this object (which is being cloned). To achieve this independence, it may be necessary to modify one or more fields of the object returned by super.clone before returning it. Typically, this means copying any mutable objects that comprise the internal "deep structure" of the object being cloned and replacing the references to these objects with references to the copies. If a class contains only primitive fields or references to immutable objects, then it is usually the case that no fields in the object returned by super.clone need to be modified.

Returns
SparseArray<E>	a clone of this instance.

contains

Added in API level 30

public boolean contains (int key)

Returns true if the key exists in the array. This is equivalent to indexOfKey(int) >= 0.

Parameters
key	int: Potential key in the mapping

Returns
boolean	true if the key is defined in the mapping

contentEquals

Added in API level 31

public boolean contentEquals (SparseArray<?> other)

Compares the contents of this SparseArray to the specified SparseArray. For backwards compatibility reasons, Object#equals(Object) cannot be implemented, so this serves as a manually invoked alternative.

Parameters
other	SparseArray: This value may be null.

Returns
boolean

contentHashCode

Added in API level 31

public int contentHashCode ()

Returns a hash code value for the contents of this SparseArray, combining the Objects#hashCode(Object) result of all its keys and values. For backwards compatibility, Object#hashCode() cannot be implemented, so this serves as a manually invoked alternative.

Returns
int

delete

Added in API level 1

public void delete (int key)

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

Parameters
key	int

get

Added in API level 1

public E get (int key)

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

Parameters
key	int

Returns
E

get

Added in API level 1

public E get (int key, 
                E valueIfKeyNotFound)

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

Parameters
key	int
valueIfKeyNotFound	E

Returns
E

indexOfKey

Added in API level 1

public int indexOfKey (int 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	int

Returns
int

indexOfValue

Added in API level 1

public int indexOfValue (E value)

Returns an index for which valueAt(int) would return the specified value, 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.

Parameters
value	E

Returns
int

keyAt

Added in API level 1

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.

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.

For indices outside of the range 0...size()-1, the behavior is undefined for apps targeting Build.VERSION_CODES.P and earlier, and an ArrayIndexOutOfBoundsException is thrown for apps targeting Build.VERSION_CODES.Q and later.

Parameters
index	int

Returns
int

put

Added in API level 1

public void put (int 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	int
value	E

remove

Added in API level 1

public void remove (int key)

Alias for delete(int).

Parameters
key	int

removeAt

Added in API level 11

public void removeAt (int index)

Removes the mapping at the specified index.

For indices outside of the range 0...size()-1, the behavior is undefined for apps targeting Build.VERSION_CODES.P and earlier, and an ArrayIndexOutOfBoundsException is thrown for apps targeting Build.VERSION_CODES.Q and later.

Parameters
index	int

removeAtRange

Added in API level 19

public void removeAtRange (int index, 
                int size)

Remove a range of mappings as a batch.

Parameters
index	int: Index to begin at
size	int: Number of mappings to remove For indices outside of the range 0...size()-1, the behavior is undefined.

set

Added in API level 31

public void set (int key, 
                E value)

Alias for put(int, java.lang.Object) to support Kotlin [index]= operator.

Parameters
key	int
value	E

See also:

• put(int, Object)

setValueAt

Added in API level 1

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 SparseArray stores.

For indices outside of the range 0...size()-1, the behavior is undefined for apps targeting Build.VERSION_CODES.P and earlier, and an ArrayIndexOutOfBoundsException is thrown for apps targeting Build.VERSION_CODES.Q and later.

Parameters
index	int
value	E

size

Added in API level 1

public int size ()

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

Returns
int

toString

Added in API level 1

public 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.

Returns
String	a string representation of the object.

valueAt

Added in API level 1

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 SparseArray 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.

For indices outside of the range 0...size()-1, the behavior is undefined for apps targeting Build.VERSION_CODES.P and earlier, and an ArrayIndexOutOfBoundsException is thrown for apps targeting Build.VERSION_CODES.Q and later.

Parameters
index	int

Returns
E