org.apache.commons.collections.map

Class IdentityMap

public class IdentityMap extends AbstractHashedMap implements Serializable, Cloneable

A Map implementation that matches keys and values based on == not equals().

This map will violate the detail of various Map and map view contracts. As a general rule, don't compare this map to other maps.

Note that IdentityMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. The simplest approach is to wrap this map using java.util.Collections#synchronizedMap(Map). This class may throw exceptions when accessed by concurrent threads without synchronization.

Since: Commons Collections 3.0

Version: $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $

Author: java util HashMap Stephen Colebourne

Nested Class Summary
protected static class	IdentityMap.IdentityEntry HashEntry

Constructor Summary
	IdentityMap() Constructs a new empty map with default size and load factor.
	IdentityMap(int initialCapacity) Constructs a new, empty map with the specified initial capacity.
	IdentityMap(int initialCapacity, float loadFactor) Constructs a new, empty map with the specified initial capacity and load factor.
	IdentityMap(Map map) Constructor copying elements from another map.

Method Summary
Object	clone() Clones the map without cloning the keys or values.
protected HashEntry	createEntry(HashEntry next, int hashCode, Object key, Object value) Creates an entry to store the data.
protected int	hash(Object key) Gets the hash code for the key specified.
protected boolean	isEqualKey(Object key1, Object key2) Compares two keys for equals.
protected boolean	isEqualValue(Object value1, Object value2) Compares two values for equals.

Constructor Detail

IdentityMap

public IdentityMap()

Constructs a new empty map with default size and load factor.

IdentityMap

public IdentityMap(int initialCapacity)

Constructs a new, empty map with the specified initial capacity.

Parameters: initialCapacity the initial capacity

Throws: IllegalArgumentException if the initial capacity is less than one

IdentityMap

public IdentityMap(int initialCapacity, float loadFactor)

Constructs a new, empty map with the specified initial capacity and load factor.

Parameters: initialCapacity the initial capacity loadFactor the load factor

Throws: IllegalArgumentException if the initial capacity is less than one IllegalArgumentException if the load factor is less than zero

IdentityMap

public IdentityMap(Map map)

Constructor copying elements from another map.

Parameters: map the map to copy

Throws: NullPointerException if the map is null

Method Detail

clone

public Object clone()

Clones the map without cloning the keys or values.

Returns: a shallow clone

createEntry

protected HashEntry createEntry(HashEntry next, int hashCode, Object key, Object value)

Creates an entry to store the data. This implementation creates an IdentityEntry instance.

Parameters: next the next entry in sequence hashCode the hash code to use key the key to store value the value to store

Returns: the newly created entry

hash

protected int hash(Object key)

Gets the hash code for the key specified. This implementation uses the identity hash code.

Parameters: key the key to get a hash code for

Returns: the hash code

isEqualKey

protected boolean isEqualKey(Object key1, Object key2)

Compares two keys for equals. This implementation uses ==.

Parameters: key1 the first key to compare key2 the second key to compare

Returns: true if equal by identity

isEqualValue

protected boolean isEqualValue(Object value1, Object value2)

Compares two values for equals. This implementation uses ==.

Parameters: value1 the first value to compare value2 the second value to compare

Returns: true if equal by identity