Package icyllis.modernui.util

Class LongSparseArray<E>

java.lang.Object

icyllis.modernui.util.LongSparseArray<E>

All Implemented Interfaces:

Cloneable

public class LongSparseArray<E>
extends Object
implements Cloneable

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).

Modified from Android.

Constructor Summary

Constructors

Constructor	Description
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.

Method Summary

Modifier and Type	Method	Description
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 key exists in the array.
boolean	containsValue(E value)	Returns true if the specified value is mapped from any key.
void	delete(long key)	Removes the mapping from the specified key, if there was any.
void	deleteAt(int index)	Removes the mapping at the specified index.
boolean	equals(Object o)
E	get(long key)	Gets the Object mapped from the specified key, or null if no such mapping has been made.
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	hashCode()
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.
int	indexOfValue(E value)	Returns an index for which valueAt(int) would return the specified value, or a negative number if no keys map to the specified value.
int	indexOfValueByValue(E value)	Returns an index for which valueAt(int) would return the specified value, or a negative number if no keys map to the specified value.
boolean	isEmpty()	Return true if size() is 0.
long	keyAt(int index)	Given an index in the range 0...size()-1, returns the key from the indexth key-value mapping that this LongSparseArray stores.
E	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 the mappings from the other to this map.
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.
E	remove(long key)	Removes the mapping from the specified key, if there was any, returning the old value.
boolean	remove(long key, Object value)	Remove an existing key from the array map only if it is currently mapped to value.
E	removeAt(int index)	Removes the mapping at the specified index and returns it.
void	removeAtRange(int index, int size)	Remove a range of mappings as a batch.
E	replace(long key, E value)	Replace the mapping for key only if it is already mapped to a value.
boolean	replace(long key, E oldValue, E newValue)	Replace the mapping for key only if it is already mapped to a value.
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 LongSparseArray stores.
int	size()	Returns the number of key-value mappings that this LongSparseArray currently stores.
String	toString()
E	valueAt(int index)	Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this LongSparseArray stores.

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Details

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.

Method Details

get

public E get(long key)

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

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.

delete

public void delete(long key)

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

remove

public E remove(long key)

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

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 - The key of the mapping to remove.

value - The value expected to be mapped to the key.

Returns:

Returns true if the mapping was removed.

deleteAt

public void deleteAt(int index)

Removes the mapping at the specified index.

Throws:

IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

removeAt

public E removeAt(int index)

Removes the mapping at the specified index and returns it.

Throws:

IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

removeAtRange

public void removeAtRange(int index,
 int size)

Remove a range of mappings as a batch.

Parameters:

index - Index to begin at

size - Number of mappings to remove

replace

@Nullable
public E replace(long key,
 E value)

Replace the mapping for key only if it is already mapped to a value.

Parameters:

key - The key of the mapping to replace.

value - The value to store for the given key.

Returns:

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 - The key of the mapping to replace.

oldValue - The value expected to be mapped to the key.

newValue - The value to store for the given key.

Returns:

Returns true if the value was replaced.

put

@Nullable
public E 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.

Returns:

Returns the previous mapped value or null.

putAll

public void putAll(@Nonnull
 LongSparseArray<? extends E> other)

Copies all 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.

putIfAbsent

@Nullable
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:

key - The key under which to store the value.

value - The value to store for the given key.

Returns:

Returns the value that was stored for the given key, or null if there was no such key.

size

public int size()

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

isEmpty

public boolean isEmpty()

Return true if size() is 0.

Returns:

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 indexth 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.

Throws:

IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

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 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.

Throws:

IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

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 LongSparseArray stores.

Throws:

IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

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.

indexOfValue

public int indexOfValue(E value)

Returns an index for which valueAt(int) would return the specified value, 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.

Note also that unlike most collections' indexOf methods, this method compares values using == rather than equals.

indexOfValueByValue

public int indexOfValueByValue(E value)

Returns an index for which valueAt(int) would return the specified value, 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.

Note also that this method uses equals unlike indexOfValue.

containsKey

public boolean containsKey(long key)

Returns true if the key exists in the array. This is equivalent to indexOfKey(long) >= 0.

Parameters:

key - Potential key in the mapping

Returns:

true if the key is defined in the mapping

containsValue

public boolean containsValue(E value)

Returns true if the specified value is mapped from any key.

clear

public void clear()

Removes all key-value mappings from this LongSparseArray.

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.

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.

Overrides:

toString in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

clone

public LongSparseArray<E> clone()

Overrides:

clone in class Object