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 | |
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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 |
E
|
get(long key)
Gets the Object mapped from the specified key, or |
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 |
int
|
indexOfValue(E value)
Returns an index for which |
boolean
|
isEmpty()
Return true if size() is 0. |
long
|
keyAt(int index)
Given an index in the range |
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 |
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 |
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 |
void
|
removeAt(int index)
Removes the mapping at the specified index. |
E
|
replace(long key, E value)
Replace the mapping for |
boolean
|
replace(long key, E oldValue, E newValue)
Replace the mapping for |
void
|
setValueAt(int index, E value)
Given an index in the range |
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 |
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.
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 | |
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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 | |
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value |
E |
Returns | |
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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 index
th 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 | |
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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 index
th 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 index
th 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 |