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 0
if no such mapping has been made.
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 keyAt(int)
would return the
specified key, or a negative number if the specified
key is not mapped.
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.
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.
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.
int
size()
Returns the number of key-value mappings that this SparseIntArray
currently stores.
String
toString()
Returns a string containing a concise, human-readable description of this
object.
This implementation composes a string by iterating over its mappings.
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.
[Expand]
Inherited Methods
From class
java.lang.Object
Public Constructors
public
SparseIntArray
(int initialCapacity)
Added in API level 1
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.
Public Methods
public
void
append
(int key, int value)
Added in API level 1
Puts a key/value pair into the array, optimizing for the case where
the key is greater than all existing keys in the array.
public
SparseIntArray
clone
()
Added in API level 1
Creates and returns a copy of this Object
. The default
implementation returns a so-called "shallow" copy: It creates a new
instance of the same class and then copies the field values (including
object references) from this instance to the new instance. A "deep" copy,
in contrast, would also recursively clone nested objects. A subclass that
needs to implement this kind of cloning should call super.clone()
to create the new instance and then create deep copies of the nested,
mutable objects.
Returns
- a copy of this object.
public
void
delete
(int key)
Added in API level 1
Removes the mapping from the specified key, if there was any.
public
int
get
(int key)
Added in API level 1
Gets the int mapped from the specified key, or 0
if no such mapping has been made.
public
int
get
(int key, int valueIfKeyNotFound)
Added in API level 1
Gets the int mapped from the specified key, or the specified value
if no such mapping has been made.
public
int
indexOfKey
(int key)
Added in API level 1
Returns the index for which keyAt(int)
would return the
specified key, or a negative number if the specified
key is not mapped.
public
int
indexOfValue
(int value)
Added in API level 1
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.
public
int
keyAt
(int index)
Added in API level 1
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.
public
void
put
(int key, int value)
Added in API level 1
Adds a mapping from the specified key to the specified value,
replacing the previous mapping from the specified key if there
was one.
public
int
size
()
Added in API level 1
Returns the number of key-value mappings that this SparseIntArray
currently stores.
public
String
toString
()
Added in API level 1
Returns a string containing a concise, human-readable description of this
object. Subclasses are encouraged to override this method and provide an
implementation that takes into account the object's type and data. The
default implementation is equivalent to the following expression:
getClass().getName() + '@' + Integer.toHexString(hashCode())
See Writing a useful
toString
method
if you intend implementing your own toString
method.
This implementation composes a string by iterating over its mappings.
Returns
- a printable representation of this object.
public
int
valueAt
(int index)
Added in API level 1
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.