org.apache.lucene.util.collections
Class ArrayHashMap<K,V>

java.lang.Object
  org.apache.lucene.util.collections.ArrayHashMap<K,V>

All Implemented Interfaces:

Iterable<V>

public class ArrayHashMap<K,V>
extends Object
implements Iterable<V>

An Array-based hashtable which maps, similar to Java's HashMap, only performance tests showed it performs better.

The hashtable is constructed with a given capacity, or 16 as a default. In case there's not enough room for new pairs, the hashtable grows. Capacity is adjusted to a power of 2, and there are 2 * capacity entries for the hash. The pre allocated arrays (for keys, values) are at length of capacity + 1, where index 0 is used as 'Ground' or 'NULL'.

The arrays are allocated ahead of hash operations, and form an 'empty space' list, to which the <key,value> pair is allocated.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Constructor Summary

ArrayHashMap()
Constructs a map with default capacity.

ArrayHashMap(int capacity)
Constructs a map with given capacity.

Method Summary

protected int	calcBaseHashIndex(K key) Calculating the baseHash index using the internal internal hashFactor.
void	clear() Empties the map.
boolean	containsKey(K key) Returns true iff the key exists in the map.
boolean	containsValue(Object o) Returns true iff the object exists in the map.
boolean	equals(Object o)
protected int	find(K key) Returns the index of the given key, or zero if the key wasn't found.
V	get(K key) Returns the object mapped with the given key, or null if the key wasn't found.
protected void	grow() Allocates a new map of double the capacity, and fast-insert the old key-value pairs.
int	hashCode()
boolean	isEmpty() Returns true iff the map is empty.
Iterator<V>	iterator() Returns an iterator on the mapped objects.
Iterator<K>	keyIterator() Returns an iterator on the map keys.
V	put(K key, V e) Inserts the <key,value> pair into the map.
V	remove(K key) Removes a <key,value> pair from the map and returns the mapped value, or null if the none existed.
int	size() Returns number of pairs currently in the map.
Object[]	toArray() Translates the mapped pairs' values into an array of Objects
V[]	toArray(V[] a) Translates the mapped pairs' values into an array of V
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

ArrayHashMap

public ArrayHashMap()

Constructs a map with default capacity.

ArrayHashMap

public ArrayHashMap(int capacity)

Constructs a map with given capacity. Capacity is adjusted to a native power of 2, with minimum of 16.

Parameters:

capacity - minimum capacity for the map.

Method Detail

calcBaseHashIndex

protected int calcBaseHashIndex(K key)

Calculating the baseHash index using the internal internal hashFactor.

clear

public void clear()

Empties the map. Generates the "Empty" space list for later allocation.

containsKey

public boolean containsKey(K key)

Returns true iff the key exists in the map.

containsValue

public boolean containsValue(Object o)

Returns true iff the object exists in the map.

find

protected int find(K key)

Returns the index of the given key, or zero if the key wasn't found.

get

public V get(K key)

Returns the object mapped with the given key, or null if the key wasn't found.

grow

protected void grow()

Allocates a new map of double the capacity, and fast-insert the old key-value pairs.

isEmpty

public boolean isEmpty()

Returns true iff the map is empty.

iterator

public Iterator<V> iterator()

Returns an iterator on the mapped objects.

Specified by:

iterator in interface Iterable<V>

keyIterator

public Iterator<K> keyIterator()

Returns an iterator on the map keys.

put

public V put(K key,
             V e)

Inserts the <key,value> pair into the map. If the key already exists, this method updates the mapped value to the given one, returning the old mapped value.

Returns:

the old mapped value, or null if the key didn't exist.

remove

public V remove(K key)

Removes a <key,value> pair from the map and returns the mapped value, or null if the none existed.

Parameters:

key - used to find the value to remove

Returns:

the removed value or null if none existed.

size

public int size()

Returns number of pairs currently in the map.

toArray

public Object[] toArray()

Translates the mapped pairs' values into an array of Objects

Returns:

an object array of all the values currently in the map.

toArray

public V[] toArray(V[] a)

Translates the mapped pairs' values into an array of V

Parameters:

a - the array into which the elements of the list are to be stored, if it is big enough; otherwise, use as much space as it can.

Returns:

an array containing the elements of the list

toString

public String toString()

Overrides:

toString in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object