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 |
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<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 |
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|---|---|
void |
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. |
@NonNull SparseArrayCompat<@NonNull E> |
clone() |
boolean |
containsKey(int key)Returns true if the specified key is mapped. |
boolean |
containsValue(@NonNull E value)Returns true if the specified value is mapped from any key. |
void |
This method is deprecated. Alias for remove(int). |
E |
get(int key)Gets the Object mapped from the specified key, or |
@NonNull E |
Gets the Object mapped from the specified |
final boolean |
Return true if |
int |
indexOfKey(int key)Returns the index for which |
int |
indexOfValue(@NonNull E value)Returns an index for which |
boolean |
isEmpty()Return true if |
int |
keyAt(int index)Given an index in the range |
void |
Adds a mapping from the specified key to the specified |
void |
putAll(@NonNull SparseArrayCompat<@NonNull E> other)Copies all of the mappings from the |
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 |
void |
remove(int key)Removes the mapping from the specified key, if there was any. |
boolean |
Remove an existing key from the array map only if it is currently mapped to |
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 the mapping for |
boolean |
Replace the mapping for |
void |
setValueAt(int index, @NonNull E value)Given an index in the range |
int |
size()Returns the number of key-value mappings that this SparseArray currently stores. |
@NonNull String |
toString()Returns a string representation of the object. |
@NonNull E |
valueAt(int index)Given an index in the range |
Extension functions |
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final boolean |
<T extends Object> SparseArrayKt.contains(Returns true if the collection contains |
final void |
<T extends Object> SparseArrayKt.forEach(Performs the given |
final @NonNull T |
<T extends Object> SparseArrayKt.getOrDefault(Return the value corresponding to |
final @NonNull T |
<T extends Object> SparseArrayKt.getOrElse(Return the value corresponding to |
final int |
SparseArrayKt.getSize(@NonNull SparseArrayCompat<@NonNull T> receiver)Returns the number of key/value pairs in the collection. |
final boolean |
<T extends Object> SparseArrayKt.isNotEmpty(Return true when the collection contains elements. |
final @NonNull IntIterator |
<T extends Object> SparseArrayKt.keyIterator(Return an iterator over the collection's keys. |
final @NonNull SparseArrayCompat<@NonNull T> |
<T extends Object> SparseArrayKt.plus(Creates a new collection by adding or replacing entries from |
final void |
<T extends Object> SparseArrayKt.set(Allows the use of the index operator for storing values in the collection. |
final @NonNull Iterator<@NonNull T> |
<T extends Object> SparseArrayKt.valueIterator(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
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.
containsKey
public boolean containsKey(int key)
Returns true if the specified key is mapped.
containsValue
public boolean containsValue(@NonNull E value)
Returns true if the specified value is mapped from any key.
get
public E get(int key)
Gets the Object mapped from the specified key, or null if no such mapping has been made.
get
public @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.
getIsEmpty
public final boolean getIsEmpty()
Return true if size is 0.
| Returns | |
|---|---|
boolean |
true if |
indexOfKey
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 |
indexOfValue
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
public boolean isEmpty()
Return true if size is 0.
| Returns | |
|---|---|
boolean |
true if |
keyAt
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
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
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
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 |
remove
public void remove(int key)
Removes the mapping from the specified key, if there was any.
remove
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 |
removeAtRange
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
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 |
replace
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 |
setValueAt
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
public int size()
Returns the number of key-value mappings that this SparseArray currently 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.