K - the type of keys maintained by this mapV - the type of mapped values
Revised by Yechiel Fefer in order to allow sparing the need to allocate an hash entry
per stored object, the value is used as an HashEntry if it is the last entry in the
linked chain per slot The original logic was preserved, main changes: -manipulating
the HashEntry externally + interface -changed the logic of "replace" functions -"put"
which is not "ifAbsent" is not supported currently (can be added if needed) - an
option of unstableKey which enforces creation of pinned HashEntry objectpublic class EconomyConcurrentHashMap<K,V> extends AbstractMap<K,V> implements IEconomyConcurrentMap<K,V>, Serializable
Hashtable, and
includes versions of methods corresponding to each method of Hashtable. However, even
though all operations are thread-safe, retrieval operations do not entail locking, and
there is not any support for locking the entire table in a way that prevents all access.
This class is fully interoperable with Hashtable in programs that rely on its thread
safety but not on its synchronization details.
Retrieval operations (including get) generally do not block, so may overlap with
update operations (including put and remove). Retrievals reflect the results of
the most recently completed update operations holding upon their onset. For aggregate
operations such as putAll and clear, concurrent retrievals may reflect
insertion or removal of only some entries. Similarly, Iterators and Enumerations return elements
reflecting the state of the hash table at some point at or since the creation of the
iterator/enumeration. They do not throw ConcurrentModificationException.
However, iterators are designed to be used by only one thread at a time.
The allowed concurrency among update operations is guided by the optional concurrencyLevel constructor argument (default 16), which is used as a hint for internal sizing. The table is internally partitioned to try to permit the indicated number of concurrent updates without contention. Because placement in hash tables is essentially random, the actual concurrency will vary. Ideally, you should choose a value to accommodate as many threads as will ever concurrently modify the table. Using a significantly higher value than you need can waste space and time, and a significantly lower value can lead to thread contention. But overestimates and underestimates within an order of magnitude do not usually have much noticeable impact. A value of one is appropriate when it is known that only one thread will modify and all others will only read. Also, resizing this or any other kind of hash table is a relatively slow operation, so, when possible, it is a good idea to provide estimates of expected table sizes in constructors.
This class and its views and iterators implement all of the optional methods of the
Map and Iterator interfaces.
Like Hashtable but unlike HashMap, this class does not allow
null to be used as a key or value.
This class is a member of the Java Collections Framework.
| Modifier and Type | Class and Description |
|---|---|
static class |
EconomyConcurrentHashMap.HashEntry<K,V>
ConcurrentHashMap list entry.
|
static class |
EconomyConcurrentHashMap.PinnedHashEntry<K,V> |
AbstractMap.SimpleEntry<K,V>| Constructor and Description |
|---|
EconomyConcurrentHashMap(IHashEntryHandler<K,V> handler)
Creates a new, empty map with a default initial capacity (16), load factor (0.75) and
concurrencyLevel (16).
|
EconomyConcurrentHashMap(int initialCapacity,
float loadFactor,
IHashEntryHandler<K,V> handler)
Creates a new, empty map with the specified initial capacity and load factor and with the
default concurrencyLevel (16).
|
EconomyConcurrentHashMap(int initialCapacity,
float loadFactor,
int concurrencyLevel,
IHashEntryHandler<K,V> handler)
Creates a new, empty map with the specified initial capacity, load factor and concurrency
level.
|
EconomyConcurrentHashMap(int initialCapacity,
IHashEntryHandler<K,V> handler)
Creates a new, empty map with the specified initial capacity, and with default load factor
(0.75) and concurrencyLevel (16).
|
EconomyConcurrentHashMap(Map<? extends K,? extends V> m,
IHashEntryHandler<K,V> handler)
Creates a new map with the same mappings as the given map.
|
| Modifier and Type | Method and Description |
|---|---|
void |
clear()
Removes all of the mappings from this map.
|
boolean |
contains(Object value)
Legacy method testing if some key maps into the specified value in this table.
|
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()
Returns a
Set view of the mappings contained in this map. |
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. |
static int |
hash(int h)
Applies a supplemental hash function to a given hashCode, which defends against poor quality
hash functions.
|
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()
Returns a
Set view of the keys contained in this map. |
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 |
putIfAbsent(K key,
V value,
boolean unstableKey)
same as putIfAbsent, but key is unstable in the hosting object, so create an pinnedhashentry
|
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) |
void |
scan() |
void |
setKeyUnstable(K key)
key may be replaced in hosting (value) object w/o calling the map prevent inconsistent
situations
|
int |
size()
Returns the number of key-value mappings in this map.
|
Collection<V> |
values()
Returns a
Collection view of the values contained in this map. |
clone, equals, hashCode, toStringfinalize, getClass, notify, notifyAll, wait, wait, waitcompute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, replaceAllpublic EconomyConcurrentHashMap(int initialCapacity,
float loadFactor,
int concurrencyLevel,
IHashEntryHandler<K,V> handler)
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.IllegalArgumentException - if the initial capacity is negative or the load factor or
concurrencyLevel are nonpositive.public EconomyConcurrentHashMap(int initialCapacity,
float loadFactor,
IHashEntryHandler<K,V> handler)
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.IllegalArgumentException - if the initial capacity of elements is negative or the load
factor is nonpositivepublic EconomyConcurrentHashMap(int initialCapacity,
IHashEntryHandler<K,V> handler)
initialCapacity - the initial capacity. The implementation performs internal sizing to
accommodate this many elements.IllegalArgumentException - if the initial capacity of elements is negative.public EconomyConcurrentHashMap(IHashEntryHandler<K,V> handler)
public EconomyConcurrentHashMap(Map<? extends K,? extends V> m, IHashEntryHandler<K,V> handler)
m - the mappublic static int hash(int h)
public boolean isEmpty()
public int size()
public V get(Object key)
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.)
get in interface Map<K,V>get in class AbstractMap<K,V>key - key whose associated value is to be returned.NullPointerException - if the specified key is nullAbstractMap.containsKey(Object)public boolean containsKey(Object key)
containsKey in interface Map<K,V>containsKey in class AbstractMap<K,V>key - possible keyNullPointerException - if the specified key is nullpublic boolean containsValue(Object value)
containsValue in interface Map<K,V>containsValue in class AbstractMap<K,V>value - value whose presence in this map is to be testedNullPointerException - if the specified value is nullpublic void scan()
public boolean contains(Object value)
containsValue(java.lang.Object), and exists solely to ensure full
compatibility with class Hashtable, which supported this method prior to
introduction of the Java Collections framework.value - a value to search forNullPointerException - if the specified value is nullpublic V put(K key, V value)
The value can be retrieved by calling the get method with a key that is equal to the original key.
put in interface Map<K,V>put in class AbstractMap<K,V>key - key with which the specified value is to be associatedvalue - value to be associated with the specified keyNullPointerException - if the specified key or value is nullpublic V putIfAbsent(K key, V value)
putIfAbsent in interface ConcurrentMap<K,V>putIfAbsent in interface Map<K,V>NullPointerException - if the specified key or value is nullpublic V putIfAbsent(K key, V value, boolean unstableKey)
putIfAbsent in interface IEconomyConcurrentMap<K,V>public void putAll(Map<? extends K,? extends V> m)
public V remove(Object key)
remove in interface Map<K,V>remove in class AbstractMap<K,V>key - the key that needs to be removedNullPointerException - if the specified key is nullpublic boolean remove(Object key, Object value)
remove in interface ConcurrentMap<K,V>remove in interface Map<K,V>NullPointerException - if the specified key is nullpublic boolean replace(K key, V oldValue, V newValue)
replace in interface ConcurrentMap<K,V>replace in interface Map<K,V>NullPointerException - if any of the arguments are nullpublic V replace(K key, V value)
replace in interface ConcurrentMap<K,V>replace in interface Map<K,V>NullPointerException - if the specified key or value is nullpublic void setKeyUnstable(K key)
setKeyUnstable in interface IEconomyConcurrentMap<K,V>public void clear()
public Set<K> keySet()
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.
The view's iterator is a "weakly consistent" iterator that will never throw
ConcurrentModificationException, and guarantees to traverse elements as they existed
upon construction of the iterator, and may (but is not guaranteed to) reflect any
modifications subsequent to construction.
public Collection<V> values()
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.
The view's iterator is a "weakly consistent" iterator that will never throw
ConcurrentModificationException, and guarantees to traverse elements as they existed
upon construction of the iterator, and may (but is not guaranteed to) reflect any
modifications subsequent to construction.
public Set<Map.Entry<K,V>> entrySet()
Set view of the mappings 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 the map, via the
Iterator.remove, Set.remove, removeAll, retainAll, and
clear operations. It does not support the add or addAll
operations.
The view's iterator is a "weakly consistent" iterator that will never throw
ConcurrentModificationException, and guarantees to traverse elements as they existed
upon construction of the iterator, and may (but is not guaranteed to) reflect any
modifications subsequent to construction.
public Enumeration<K> keys()
keySet()public Enumeration<V> elements()
values()Copyright © GigaSpaces.