dsto.dfc.collections
Class IdentityHashMap

java.lang.Object
  java.util.AbstractMap
      dsto.dfc.collections.IdentityHashMap

All Implemented Interfaces:

Serializable, Cloneable, Map

public class IdentityHashMap
extends AbstractMap
implements Map, Cloneable, Serializable

Exactly like HashMap except keys and entries are considered equal only if they are the same object (ie equals using == instead of equals ()).

Version:

$Revision$

Author:

mpp

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Field Summary

protected int	count The total number of mappings in the hash table.
protected float	loadFactor The load factor for the hashtable.
protected int	modCount The number of times this IdentityHashMap has been structurally modified Structural modifications are those that change the number of mappings in the IdentityHashMap or otherwise modify its internal structure (e.g., rehash).
protected dsto.dfc.collections.IdentityHashMap.Entry[]	table The hash table data.
protected int	threshold The table is rehashed when its size exceeds this threshold.

Constructor Summary

IdentityHashMap()
Constructs a new, empty map with a default capacity and load factor, which is 0.75.

IdentityHashMap(int initialCapacity)
Constructs a new, empty map with the specified initial capacity and default load factor, which is 0.75.

IdentityHashMap(int initialCapacity, float loadFactor)
Constructs a new, empty map with the specified initial capacity and the specified load factor.

IdentityHashMap(Map t)
Constructs a new map with the same mappings as the given map.

Method Summary

void	clear() Removes all mappings from this map.
Object	clone() Returns a shallow copy of this IdentityHashMap instance: the keys and values themselves are not cloned.
boolean	containsKey(Object key) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(Object value) Returns true if this map maps one or more keys to the specified value.
Set	entrySet() Returns a collection view of the mappings contained in this map.
Object	get(Object key) Returns the value to which this map maps the specified key.
protected Iterator	getHashIterator(int type)
boolean	isEmpty() Returns true if this map contains no key-value mappings.
Set	keySet() Returns a set view of the keys contained in this map.
Object	put(Object key, Object value) Associates the specified value with the specified key in this map.
void	putAll(Map t) Copies all of the mappings from the specified map to this one.
Object	remove(Object key) Removes the mapping for this key from this map if present.
int	size() Returns the number of key-value mappings in this map.
Collection	values() Returns a collection view of the values contained in this map.

Methods inherited from class java.util.AbstractMap

equals, hashCode, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

equals, hashCode

Field Detail

table

protected transient dsto.dfc.collections.IdentityHashMap.Entry[] table

The hash table data.

count

protected transient int count

The total number of mappings in the hash table.

threshold

protected int threshold

The table is rehashed when its size exceeds this threshold. (The value of this field is (int) (capacity * loadFactor).)

loadFactor

protected float loadFactor

The load factor for the hashtable.

modCount

protected transient int modCount

The number of times this IdentityHashMap has been structurally modified Structural modifications are those that change the number of mappings in the IdentityHashMap or otherwise modify its internal structure (e.g., rehash). This field is used to make iterators on Collection-views of the IdentityHashMap fail-fast. (See ConcurrentModificationException).

Constructor Detail

IdentityHashMap

public IdentityHashMap(int initialCapacity,
                       float loadFactor)

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

Parameters:

initialCapacity - the initial capacity of the IdentityHashMap.

loadFactor - the load factor of the IdentityHashMap

Throws:

IllegalArgumentException - if the initial capacity is less than zero, or if the load factor is nonpositive.

IdentityHashMap

public IdentityHashMap(int initialCapacity)

Constructs a new, empty map with the specified initial capacity and default load factor, which is 0.75.

Parameters:

initialCapacity - the initial capacity of the IdentityHashMap.

Throws:

IllegalArgumentException - if the initial capacity is less than zero.

IdentityHashMap

public IdentityHashMap()

Constructs a new, empty map with a default capacity and load factor, which is 0.75.

IdentityHashMap

public IdentityHashMap(Map t)

Constructs a new map with the same mappings as the given map. The map is created with a capacity of twice the number of mappings in the given map or 11 (whichever is greater), and a default load factor, which is 0.75.

Parameters:

t - the map whose mappings are to be placed in this map.

Method Detail

size

public int size()

Returns the number of key-value mappings in this map.

Specified by:

size in interface Map

Overrides:

size in class AbstractMap

Returns:

the number of key-value mappings in this map.

isEmpty

public boolean isEmpty()

Returns true if this map contains no key-value mappings.

Specified by:

isEmpty in interface Map

Overrides:

isEmpty in class AbstractMap

Returns:

true if this map contains no key-value mappings.

containsValue

public boolean containsValue(Object value)

Returns true if this map maps one or more keys to the specified value.

Specified by:

containsValue in interface Map

Overrides:

containsValue in class AbstractMap

Parameters:

value - value whose presence in this map is to be tested.

Returns:

true if this map maps one or more keys to the specified value.

containsKey

public boolean containsKey(Object key)

Returns true if this map contains a mapping for the specified key.

Specified by:

containsKey in interface Map

Overrides:

containsKey in class AbstractMap

Parameters:

key - key whose presence in this Map is to be tested.

Returns:

true if this map contains a mapping for the specified key.

get

public Object get(Object key)

Returns the value to which this map maps the specified key. Returns null if the map contains no mapping for this key. A return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

Specified by:

get in interface Map

Overrides:

get in class AbstractMap

Parameters:

key - key whose associated value is to be returned.

Returns:

the value to which this map maps the specified key.

put

public Object put(Object key,
                  Object value)

Associates the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced.

Specified by:

put in interface Map

Overrides:

put in class AbstractMap

Parameters:

key - key with which the specified value is to be associated.

value - value to be associated with the specified key.

Returns:

previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the IdentityHashMap previously associated null with the specified key.

remove

public Object remove(Object key)

Removes the mapping for this key from this map if present.

Specified by:

remove in interface Map

Overrides:

remove in class AbstractMap

Parameters:

key - key whose mapping is to be removed from the map.

Returns:

previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key.

putAll

public void putAll(Map t)

Copies all of the mappings from the specified map to this one. These mappings replace any mappings that this map had for any of the keys currently in the specified Map.

Specified by:

putAll in interface Map

Overrides:

putAll in class AbstractMap

Parameters:

t - Mappings to be stored in this map.

clear

public void clear()

Removes all mappings from this map.

Specified by:

clear in interface Map

Overrides:

clear in class AbstractMap

clone

public Object clone()

Returns a shallow copy of this IdentityHashMap instance: the keys and values themselves are not cloned.

Overrides:

clone in class AbstractMap

Returns:

a shallow copy of this map.

keySet

public Set keySet()

Returns a set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. The set supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

keySet in interface Map

Overrides:

keySet in class AbstractMap

Returns:

a set view of the keys contained in this map.

values

public Collection values()

Returns a collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

values in interface Map

Overrides:

values in class AbstractMap

Returns:

a collection view of the values contained in this map.

entrySet

public Set entrySet()

Returns a collection view of the mappings contained in this map. Each element in the returned collection is a Map.Entry. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

entrySet in interface Map

Specified by:

entrySet in class AbstractMap

Returns:

a collection view of the mappings contained in this map.

See Also:

Map.Entry

getHashIterator

protected Iterator getHashIterator(int type)