edu.ucla.sspace.util

Class HashIndexer<T>

java.lang.Object

edu.ucla.sspace.util.HashIndexer<T>

All Implemented Interfaces:

Indexer<T>, Serializable, Iterable<Map.Entry<T,Integer>>

public class HashIndexer<T>
extends Object
implements Indexer<T>, Serializable

A utility class for mapping a set of objects to unique indices based on object equality. The indices returned by this class will always begin at 0.

This implementation provides faster index(Object) performance than ObjectIndexer but at the expensive of having amortized constant time lookup(int) and #find(int) performance. This class will have superior performance in use cases where all objects are indexed and then lookup or find is called repeatedly whithout having indexed any new objects.

See Also:

ObjectIndexer, Serialized Form

Constructor Summary

Constructors

Constructor and Description
HashIndexer() Creates an empty HashIndexer with no mappings.
HashIndexer(Collection<? extends T> items) Creates an HashIndexer with indices for all of the provided items.
HashIndexer(Indexer<? extends T> indexed) Creates an HashIndexer with indices for all of the provided items.

Method Summary

Methods

Modifier and Type	Method and Description
void	clear() Removes all of the item-index mappings.
boolean	contains(T item) Returns true if the item has a corresponding index
int	find(T item) Returns the index for the item or a negative value corresponding to the index the object would have been assigned if it had been added.
int	highestIndex() Returns the highest index to which any element is mapped.
int	index(T item) Adds the item and creates an index for it, returning that index.
boolean	indexAll(Collection<T> items) Adds an index for each item in the collection if it did not already exist, returning true if at least one new index was added.
Set<T>	items() Returns an unmodifiable view of the items currently mapped to indices
Iterator<Map.Entry<T,Integer>>	iterator() Returns an iterator over all the objects and their corresponding indices.
T	lookup(int index) Returns the element to which this index is mapped or null if the index has not been mapped
Map<Integer,T>	mapping() Returns an unmodifiable view from each index to the object mapped to that index.
int	size() Returns the number of items that are mapped to indices.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

HashIndexer

public HashIndexer()

Creates an empty HashIndexer with no mappings.

HashIndexer

public HashIndexer(Collection<? extends T> items)

Creates an HashIndexer with indices for all of the provided items.

HashIndexer

public HashIndexer(Indexer<? extends T> indexed)

Creates an HashIndexer with indices for all of the provided items.

Method Detail

clear

public void clear()

Removes all of the item-index mappings.

Specified by:

clear in interface Indexer<T>

contains

public boolean contains(T item)

Returns true if the item has a corresponding index

Specified by:

contains in interface Indexer<T>

items

public Set<T> items()

Returns an unmodifiable view of the items currently mapped to indices

Specified by:

items in interface Indexer<T>

find

public int find(T item)

Returns the index for the item or a negative value corresponding to the index the object would have been assigned if it had been added.

Specified by:

find in interface Indexer<T>

highestIndex

public int highestIndex()

Returns the highest index to which any element is mapped.

Specified by:

highestIndex in interface Indexer<T>

index

public int index(T item)

Adds the item and creates an index for it, returning that index.

Specified by:

index in interface Indexer<T>

indexAll

public boolean indexAll(Collection<T> items)

Adds an index for each item in the collection if it did not already exist, returning true if at least one new index was added.

Specified by:

indexAll in interface Indexer<T>

iterator

public Iterator<Map.Entry<T,Integer>> iterator()

Returns an iterator over all the objects and their corresponding indices. The returned iterator does not support remove. The returned iterator does not support remove.

Specified by:

iterator in interface Indexer<T>

Specified by:

iterator in interface Iterable<Map.Entry<T,Integer>>

lookup

public T lookup(int index)

Returns the element to which this index is mapped or null if the index has not been mapped

Specified by:

lookup in interface Indexer<T>

mapping

public Map<Integer,T> mapping()

Returns an unmodifiable view from each index to the object mapped to that index.

Specified by:

mapping in interface Indexer<T>

size

public int size()

Returns the number of items that are mapped to indices.

Specified by:

size in interface Indexer<T>

toString

public String toString()

Overrides:

toString in class Object