freemarker.ext.util

Class IdentityHashMap

Implemented Interfaces:
Cloneable, Map, java.io.Serializable

public class IdentityHashMap
extends AbstractMap
implements Map, Cloneable, java.io.Serializable

A variant of java.util.HashMap that uses System.identityHashCode(Object) for hashing, and reference comparison instead of Object.equals(Object). Note that this applies only to keys, and not to values, i.e. containsValue(Object) still uses Object.equals(Object).
Author:
Attila Szegedi
See Also:
Serialized Form

Field Summary

static long
serialVersionUID

Constructor Summary

IdentityHashMap()
Constructs a new, empty map with a default capacity and load factor, which is 0.75.
IdentityHashMap(Map t)
Constructs a new map with the same mappings as the given map.
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.

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.
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.

Field Details

serialVersionUID

public static final long serialVersionUID
Field Value:
362498820763181265L

Constructor Details

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.

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.

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

Method Details

clear

public void clear()
Removes all mappings from this map.

clone

public Object clone()
Returns a shallow copy of this IdentityHashMap instance: the keys and values themselves are not cloned.
Returns:
a shallow copy of this map.

containsKey

public boolean containsKey(Object key)
Returns true if this map contains a mapping for the specified key.
Parameters:
key - key whose presence in this Map is to be tested.
Returns:
true if this map contains a mapping for the specified key.

containsValue

public boolean containsValue(Object value)
Returns true if this map maps one or more keys to the specified value.
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.

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.
Returns:
a collection view of the mappings contained in this map.
See Also:
java.util.Map.Entry

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.
Parameters:
key - key whose associated value is to be returned.
Returns:
the value to which this map maps the specified key.

isEmpty

public boolean isEmpty()
Returns true if this map contains no key-value mappings.
Returns:
true if this map contains no key-value mappings.

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.
Returns:
a set view of the keys contained in this map.

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.
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.

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.
Parameters:
t - Mappings to be stored in this map.

remove

public Object remove(Object key)
Removes the mapping for this key from this map if present.
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.

size

public int size()
Returns the number of key-value mappings in this map.
Returns:
the number of key-value mappings 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.
Returns:
a collection view of the values contained in this map.