SparseIntArray
public
class
SparseIntArray
extends Object
implements
Cloneable
java.lang.Object | |
↳ | android.util.SparseIntArray |
SparseIntArrays map integers to integers. Unlike a normal array of integers, there can be gaps in the indices. It is intended to be more memory efficient than using a HashMap to map Integers to Integers, both because it avoids auto-boxing keys and values 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%.
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 | |
---|---|
SparseIntArray()
Creates a new SparseIntArray containing no mappings. |
|
SparseIntArray(int initialCapacity)
Creates a new SparseIntArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings. |
Public methods | |
---|---|
void
|
append(int key, int 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 SparseIntArray. |
SparseIntArray
|
clone()
Creates and returns a copy of this object. |
void
|
delete(int key)
Removes the mapping from the specified key, if there was any. |
int
|
get(int key)
Gets the int mapped from the specified key, or |
int
|
get(int key, int valueIfKeyNotFound)
Gets the int mapped from the specified key, or the specified value if no such mapping has been made. |
int
|
indexOfKey(int key)
Returns the index for which |
int
|
indexOfValue(int value)
Returns an index for which |
int
|
keyAt(int index)
Given an index in the range |
void
|
put(int key, int 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
|
removeAt(int index)
Removes the mapping at the given index. |
void
|
setValueAt(int index, int value)
Directly set the value at a particular index. |
int
|
size()
Returns the number of key-value mappings that this SparseIntArray currently stores. |
String
|
toString()
Returns a string representation of the object. This implementation composes a string by iterating over its mappings. |
int
|
valueAt(int index)
Given an index in the range |
Inherited methods | |
---|---|
Public constructors
SparseIntArray
public SparseIntArray ()
Creates a new SparseIntArray containing no mappings.
SparseIntArray
public SparseIntArray (int initialCapacity)
Creates a new SparseIntArray 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 (int key, int 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 |
int |
clear
public void clear ()
Removes all key-value mappings from this SparseIntArray.
clone
public SparseIntArray 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:
will be true, and that the expression: x.clone() != x
will be x.clone().getClass() == x.getClass()
true
, but these are not absolute requirements.
While it is typically the case that:
will be x.clone().equals(x)
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 | |
---|---|
SparseIntArray |
a clone of this instance. |
delete
public void delete (int key)
Removes the mapping from the specified key, if there was any.
Parameters | |
---|---|
key |
int |
get
public int get (int key)
Gets the int mapped from the specified key, or 0
if no such mapping has been made.
Parameters | |
---|---|
key |
int |
Returns | |
---|---|
int |
get
public int get (int key, int valueIfKeyNotFound)
Gets the int mapped from the specified key, or the specified value if no such mapping has been made.
Parameters | |
---|---|
key |
int |
valueIfKeyNotFound |
int |
Returns | |
---|---|
int |
indexOfKey
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
public int indexOfValue (int 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 |
int |
Returns | |
---|---|
int |
keyAt
public int keyAt (int index)
Given an index in the range 0...size()-1
, returns
the key from the index
th key-value mapping that this
SparseIntArray 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
public void put (int key, int 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 |
int |
removeAt
public void removeAt (int index)
Removes the mapping at the given index.
Parameters | |
---|---|
index |
int |
setValueAt
public void setValueAt (int index, int value)
Directly set the value at a particular 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 |
value |
int |
size
public int size ()
Returns the number of key-value mappings that this SparseIntArray currently stores.
Returns | |
---|---|
int |
toString
public String toString ()
Returns a string representation of the object.
This implementation composes a string by iterating over its mappings.
Returns | |
---|---|
String |
a string representation of the object. |
valueAt
public int valueAt (int index)
Given an index in the range 0...size()-1
, returns
the value from the index
th key-value mapping that this
SparseIntArray 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 | |
---|---|
int |