org.apache.commons.collections.map
Class IdentityMap

java.lang.Object
  java.util.AbstractMap
      org.apache.commons.collections.map.AbstractHashedMap
          org.apache.commons.collections.map.IdentityMap

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, java.util.Map, IterableMap

public class IdentityMap
extends AbstractHashedMap
implements java.io.Serializable, java.lang.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 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

See Also:

Serialized Form

Nested Class Summary

protected static class

IdentityMap.IdentityEntry HashEntry

Nested classes/interfaces inherited from class org.apache.commons.collections.map.AbstractHashedMap

AbstractHashedMap.EntrySet, AbstractHashedMap.EntrySetIterator, AbstractHashedMap.HashEntry, AbstractHashedMap.HashIterator, AbstractHashedMap.HashMapIterator, AbstractHashedMap.KeySet, AbstractHashedMap.KeySetIterator, AbstractHashedMap.Values, AbstractHashedMap.ValuesIterator

Nested classes/interfaces inherited from interface java.util.Map

java.util.Map.Entry

Field Summary

Fields inherited from class org.apache.commons.collections.map.AbstractHashedMap

data, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD, entrySet, GETKEY_INVALID, GETVALUE_INVALID, keySet, loadFactor, MAXIMUM_CAPACITY, modCount, NO_NEXT_ENTRY, NO_PREVIOUS_ENTRY, NULL, REMOVE_INVALID, SETVALUE_INVALID, size, threshold, values

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(java.util.Map map)
Constructor copying elements from another map.

Method Summary

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

Methods inherited from class org.apache.commons.collections.map.AbstractHashedMap

addEntry, addMapping, calculateNewCapacity, calculateThreshold, checkCapacity, clear, containsKey, containsValue, convertKey, createEntrySetIterator, createKeySetIterator, createValuesIterator, destroyEntry, doReadObject, doWriteObject, ensureCapacity, entryHashCode, entryKey, entryNext, entrySet, entryValue, equals, get, getEntry, hashCode, hashIndex, init, isEmpty, keySet, mapIterator, put, putAll, remove, removeEntry, removeMapping, reuseEntry, size, toString, updateEntry, values

Methods inherited from class java.lang.Object

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

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:

java.lang.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:

java.lang.IllegalArgumentException - if the initial capacity is less than one

java.lang.IllegalArgumentException - if the load factor is less than zero

IdentityMap

public IdentityMap(java.util.Map map)

Constructor copying elements from another map.

Parameters:

map - the map to copy

Throws:

java.lang.NullPointerException - if the map is null

Method Detail

hash

protected int hash(java.lang.Object key)

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

Overrides:

hash in class AbstractHashedMap

Parameters:

key - the key to get a hash code for

Returns:

the hash code

isEqualKey

protected boolean isEqualKey(java.lang.Object key1,
                             java.lang.Object key2)

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

Overrides:

isEqualKey in class AbstractHashedMap

Parameters:

key1 - the first key to compare

key2 - the second key to compare

Returns:

true if equal by identity

isEqualValue

protected boolean isEqualValue(java.lang.Object value1,
                               java.lang.Object value2)

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

Overrides:

isEqualValue in class AbstractHashedMap

Parameters:

value1 - the first value to compare

value2 - the second value to compare

Returns:

true if equal by identity

createEntry

protected AbstractHashedMap.HashEntry createEntry(AbstractHashedMap.HashEntry next,
                                                  int hashCode,
                                                  java.lang.Object key,
                                                  java.lang.Object value)

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

Overrides:

createEntry in class AbstractHashedMap

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

clone

public java.lang.Object clone()

Clones the map without cloning the keys or values.

Overrides:

clone in class AbstractHashedMap

Returns:

a shallow clone