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Android APIs
public class

SparseBooleanArray

extends Object
implements Cloneable
java.lang.Object
   ↳ android.util.SparseBooleanArray

Class Overview

SparseBooleanArrays map integers to booleans. Unlike a normal array of booleans there can be gaps in the indices. It is intended to be more memory efficient than using a HashMap to map Integers to Booleans, 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
SparseBooleanArray()
Creates a new SparseBooleanArray containing no mappings.
SparseBooleanArray(int initialCapacity)
Creates a new SparseBooleanArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings.
Public Methods
void append(int key, boolean 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 SparseBooleanArray.
SparseBooleanArray clone()
Creates and returns a copy of this Object.
void delete(int key)
Removes the mapping from the specified key, if there was any.
boolean get(int key)
Gets the boolean mapped from the specified key, or false if no such mapping has been made.
boolean get(int key, boolean valueIfKeyNotFound)
Gets the boolean 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(boolean 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 indexth key-value mapping that this SparseBooleanArray stores.
void put(int key, boolean value)
Adds a mapping from the specified key to the specified value, replacing the previous mapping from the specified key if there was one.
int size()
Returns the number of key-value mappings that this SparseBooleanArray 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.

boolean valueAt(int index)
Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this SparseBooleanArray stores.
[Expand]
Inherited Methods
From class java.lang.Object

Public Constructors

public SparseBooleanArray ()

Added in API level 1

Creates a new SparseBooleanArray containing no mappings.

public SparseBooleanArray (int initialCapacity)

Added in API level 1

Creates a new SparseBooleanArray 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, boolean 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 void clear ()

Added in API level 1

Removes all key-value mappings from this SparseBooleanArray.

public SparseBooleanArray 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 boolean get (int key)

Added in API level 1

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

public boolean get (int key, boolean valueIfKeyNotFound)

Added in API level 1

Gets the boolean 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 (boolean 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 indexth key-value mapping that this SparseBooleanArray 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, boolean 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 SparseBooleanArray 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 boolean valueAt (int index)

Added in API level 1

Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this SparseBooleanArray 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.