Package org.jf.util

Class SparseArray<E>

java.lang.Object

org.jf.util.SparseArray<E>

public class SparseArray<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 efficient than using a HashMap to map Integers to Objects.

Field Summary

Fields

Modifier and Type	Field	Description
private static final Object	DELETED
private boolean	mGarbage
private int[]	mKeys
private int	mSize
private Object[]	mValues

Constructor Summary

Constructors

Constructor	Description
SparseArray()	Creates a new SparseArray containing no mappings.
SparseArray(int initialCapacity)	Creates a new SparseArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings.

Method Summary

Modifier and Type	Method	Description
void	append(int 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.
private static int	binarySearch(int[] a, int start, int len, int key)
void	clear()	Removes all key-value mappings from this SparseArray.
void	delete(int key)	Removes the mapping from the specified key, if there was any.
void	ensureCapacity(int capacity)	Increases the size of the underlying storage if needed, to ensure that it can hold the specified number of items without having to allocate additional memory
private void	gc()
E	get(int key)	Gets the Object mapped from the specified key, or null if no such mapping has been made.
E	get(int key, E valueIfKeyNotFound)	Gets the Object mapped from the specified key, or the specified Object if no such mapping has been made.
List<E>	getValues()
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(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.
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.
void	put(int 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	remove(int key)	Alias for delete(int).
void	setValueAt(int index, 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.
int	size()	Returns the number of key-value mappings that this SparseArray currently stores.
E	valueAt(int index)	Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this SparseArray stores.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

DELETED

private static final Object DELETED

mGarbage

private boolean mGarbage

mKeys

private int[] mKeys

mValues

private Object[] mValues

mSize

private int mSize

Constructor Details

SparseArray

public SparseArray()

Creates a new SparseArray containing no mappings.

SparseArray

public SparseArray(int initialCapacity)

Creates a new SparseArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings.

Method Details

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 E get(int key,
 E valueIfKeyNotFound)

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

delete

public void delete(int key)

Removes the mapping from the specified key, if there was any.

remove

public void remove(int key)

Alias for delete(int).

gc

private void gc()

put

public void put(int 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.

size

public int size()

Returns the number of key-value mappings that this SparseArray currently stores.

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.

valueAt

public E valueAt(int index)

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

setValueAt

public void setValueAt(int index,
 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.

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.

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.

clear

public void clear()

Removes all key-value mappings from this SparseArray.

append

public void append(int 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.

ensureCapacity

public void ensureCapacity(int capacity)

Increases the size of the underlying storage if needed, to ensure that it can hold the specified number of items without having to allocate additional memory

Parameters:

capacity - the number of items

binarySearch

private static int binarySearch(int[] a,
 int start,
 int len,
 int key)

getValues

public List<E> getValues()

Returns:

a read-only list of the values in this SparseArray which are in ascending order, based on their associated key