com.alibaba.druid.util
Class ConcurrentIdentityHashMap<K,V>

java.lang.Object
  java.util.AbstractMap<K,V>
      com.alibaba.druid.util.ConcurrentIdentityHashMap<K,V>

Type Parameters:

K - the type of keys maintained by this map

V - the type of mapped values

All Implemented Interfaces:

ConcurrentMap<K,V>, Map<K,V>

public class ConcurrentIdentityHashMap<K,V>
extends AbstractMap<K,V>
implements ConcurrentMap<K,V>

An alternative identity-comparing ConcurrentMap which is similar to ConcurrentHashMap.

Version:

$Rev: 2217 $, $Date: 2010-03-16 18:39:56 +0900 (Tue, 16 Mar 2010) $

Author:

The Netty Project, Doug Lea, Jason T. Greene, Trustin Lee

Nested Class Summary

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

AbstractMap.SimpleImmutableEntry<K,V>

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

Map.Entry<K,V>

Constructor Summary

ConcurrentIdentityHashMap()
Creates a new, empty map with a default initial capacity (16), reference types (weak keys, strong values), default load factor (0.75) and concurrencyLevel (16).

ConcurrentIdentityHashMap(int initialCapacity)
Creates a new, empty map with the specified initial capacity, and with default reference types (weak keys, strong values), load factor (0.75) and concurrencyLevel (16).

ConcurrentIdentityHashMap(int initialCapacity, float loadFactor)
Creates a new, empty map with the specified initial capacity and load factor and with the default reference types (weak keys, strong values), and concurrencyLevel (16).

ConcurrentIdentityHashMap(int initialCapacity, float loadFactor, int concurrencyLevel)
Creates a new, empty map with the specified initial capacity, load factor and concurrency level.

ConcurrentIdentityHashMap(Map<? extends K,? extends V> m)
Creates a new map with the same mappings as the given map.

Method Summary

void	clear() Removes all of the mappings from this map.
boolean	contains(Object value)
boolean	containsKey(Object key) Tests if the specified object is a key in this table.
boolean	containsValue(Object value) Returns true if this map maps one or more keys to the specified value.
Enumeration<V>	elements() Returns an enumeration of the values in this table.
Set<Map.Entry<K,V>>	entrySet()
V	get(Object key) Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
boolean	isEmpty() Returns true if this map contains no key-value mappings.
Enumeration<K>	keys() Returns an enumeration of the keys in this table.
Set<K>	keySet()
V	put(K key, V value) Maps the specified key to the specified value in this table.
void	putAll(Map<? extends K,? extends V> m) Copies all of the mappings from the specified map to this one.
V	putIfAbsent(K key, V value)
V	remove(Object key) Removes the key (and its corresponding value) from this map.
boolean	remove(Object key, Object value)
V	replace(K key, V value)
boolean	replace(K key, V oldValue, V newValue)
int	size() Returns the number of key-value mappings in this map.
Collection<V>	values()

Methods inherited from class java.util.AbstractMap

equals, hashCode, toString

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

equals, hashCode

Constructor Detail

ConcurrentIdentityHashMap

public ConcurrentIdentityHashMap(int initialCapacity,
                                 float loadFactor,
                                 int concurrencyLevel)

Creates a new, empty map with the specified initial capacity, load factor and concurrency level.

Parameters:

initialCapacity - the initial capacity. The implementation performs internal sizing to accommodate this many elements.

loadFactor - the load factor threshold, used to control resizing. Resizing may be performed when the average number of elements per bin exceeds this threshold.

concurrencyLevel - the estimated number of concurrently updating threads. The implementation performs internal sizing to try to accommodate this many threads.

Throws:

IllegalArgumentException - if the initial capacity is negative or the load factor or concurrencyLevel are nonpositive.

ConcurrentIdentityHashMap

public ConcurrentIdentityHashMap(int initialCapacity,
                                 float loadFactor)

Creates a new, empty map with the specified initial capacity and load factor and with the default reference types (weak keys, strong values), and concurrencyLevel (16).

Parameters:

initialCapacity - The implementation performs internal sizing to accommodate this many elements.

loadFactor - the load factor threshold, used to control resizing. Resizing may be performed when the average number of elements per bin exceeds this threshold.

Throws:

IllegalArgumentException - if the initial capacity of elements is negative or the load factor is nonpositive

ConcurrentIdentityHashMap

public ConcurrentIdentityHashMap(int initialCapacity)

Creates a new, empty map with the specified initial capacity, and with default reference types (weak keys, strong values), load factor (0.75) and concurrencyLevel (16).

Parameters:

initialCapacity - the initial capacity. The implementation performs internal sizing to accommodate this many elements.

Throws:

IllegalArgumentException - if the initial capacity of elements is negative.

ConcurrentIdentityHashMap

public ConcurrentIdentityHashMap()

Creates a new, empty map with a default initial capacity (16), reference types (weak keys, strong values), default load factor (0.75) and concurrencyLevel (16).

ConcurrentIdentityHashMap

public ConcurrentIdentityHashMap(Map<? extends K,? extends V> m)

Creates a new map with the same mappings as the given map. The map is created with a capacity of 1.5 times the number of mappings in the given map or 16 (whichever is greater), and a default load factor (0.75) and concurrencyLevel (16).

Parameters:

m - the map

Method Detail

isEmpty

public boolean isEmpty()

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

Specified by:

isEmpty in interface Map<K,V>

Overrides:

isEmpty in class AbstractMap<K,V>

Returns:

true if this map contains no key-value mappings

size

public int size()

Returns the number of key-value mappings in this map. If the map contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

Specified by:

size in interface Map<K,V>

Overrides:

size in class AbstractMap<K,V>

Returns:

the number of key-value mappings in this map

get

public V get(Object key)

Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

More formally, if this map contains a mapping from a key k to a value v such that key.equals(k), then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

Specified by:

get in interface Map<K,V>

Overrides:

get in class AbstractMap<K,V>

Throws:

NullPointerException - if the specified key is null

containsKey

public boolean containsKey(Object key)

Tests if the specified object is a key in this table.

Specified by:

containsKey in interface Map<K,V>

Overrides:

containsKey in class AbstractMap<K,V>

Parameters:

key - possible key

Returns:

true if and only if the specified object is a key in this table, as determined by the equals method; false otherwise.

Throws:

NullPointerException - if the specified key is null

containsValue

public boolean containsValue(Object value)

Returns true if this map maps one or more keys to the specified value. Note: This method requires a full internal traversal of the hash table, and so is much slower than method containsKey.

Specified by:

containsValue in interface Map<K,V>

Overrides:

containsValue in class AbstractMap<K,V>

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

Throws:

NullPointerException - if the specified value is null

contains

public boolean contains(Object value)

put

public V put(K key,
             V value)

Maps the specified key to the specified value in this table. Neither the key nor the value can be null.

The value can be retrieved by calling the get method with a key that is equal to the original key.

Specified by:

put in interface Map<K,V>

Overrides:

put in class AbstractMap<K,V>

Parameters:

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

value - value to be associated with the specified key

Returns:

the previous value associated with key, or null if there was no mapping for key

Throws:

NullPointerException - if the specified key or value is null

putIfAbsent

public V putIfAbsent(K key,
                     V value)

Specified by:

putIfAbsent in interface ConcurrentMap<K,V>

Returns:

the previous value associated with the specified key, or null if there was no mapping for the key

Throws:

NullPointerException - if the specified key or value is null

putAll

public final void putAll(Map<? extends K,? extends V> m)

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<K,V>

Overrides:

putAll in class AbstractMap<K,V>

Parameters:

m - mappings to be stored in this map

remove

public V remove(Object key)

Removes the key (and its corresponding value) from this map. This method does nothing if the key is not in the map.

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class AbstractMap<K,V>

Parameters:

key - the key that needs to be removed

Returns:

the previous value associated with key, or null if there was no mapping for key

Throws:

NullPointerException - if the specified key is null

remove

public boolean remove(Object key,
                      Object value)

Specified by:

remove in interface ConcurrentMap<K,V>

Throws:

NullPointerException - if the specified key is null

replace

public boolean replace(K key,
                       V oldValue,
                       V newValue)

Specified by:

replace in interface ConcurrentMap<K,V>

Throws:

NullPointerException - if any of the arguments are null

replace

public V replace(K key,
                 V value)

Specified by:

replace in interface ConcurrentMap<K,V>

Returns:

the previous value associated with the specified key, or null if there was no mapping for the key

Throws:

NullPointerException - if the specified key or value is null

clear

public void clear()

Removes all of the mappings from this map.

Specified by:

clear in interface Map<K,V>

Overrides:

clear in class AbstractMap<K,V>

keySet

public Set<K> keySet()

Specified by:

keySet in interface Map<K,V>

Overrides:

keySet in class AbstractMap<K,V>

values

public Collection<V> values()

Specified by:

values in interface Map<K,V>

Overrides:

values in class AbstractMap<K,V>

entrySet

public Set<Map.Entry<K,V>> entrySet()

Specified by:

entrySet in interface Map<K,V>

Specified by:

entrySet in class AbstractMap<K,V>

keys

public Enumeration<K> keys()

Returns an enumeration of the keys in this table.

Returns:

an enumeration of the keys in this table

See Also:

keySet()

elements

public Enumeration<V> elements()

Returns an enumeration of the values in this table.

Returns:

an enumeration of the values in this table

See Also:

values()