org.jupiter.common.concurrent.collection

类 NonBlockingHashMap<TypeK,TypeV>

java.lang.Object

java.util.AbstractMap<TypeK,TypeV>

org.jupiter.common.concurrent.collection.NonBlockingHashMap<TypeK,TypeV>

类型参数:

TypeK - the type of keys maintained by this map

TypeV - the type of mapped values

所有已实现的接口:

Serializable, Cloneable, ConcurrentMap<TypeK,TypeV>, Map<TypeK,TypeV>

public class NonBlockingHashMap<TypeK,TypeV>
extends AbstractMap<TypeK,TypeV>
implements ConcurrentMap<TypeK,TypeV>, Cloneable, Serializable

A lock-free alternate implementation of ConcurrentHashMap with better scaling properties and generally lower costs to mutate the Map. It provides identical correctness properties as ConcurrentHashMap. All operations are non-blocking and multi-thread safe, including all update operations. NonBlockingHashMap scales substantially better than ConcurrentHashMap for high update rates, even with a large concurrency factor. Scaling is linear up to 768 CPUs on a 768-CPU Azul box, even with 100% updates or 100% reads or any fraction in-between. Linear scaling up to all cpus has been observed on a 32-way Sun US2 box, 32-way Sun Niagara box, 8-way Intel box and a 4-way Power box.

This class obeys the same functional specification as Hashtable, and includes versions of methods corresponding to each method of Hashtable. However, even though all operations are thread-safe, 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.

Operations (including put) generally do not block, so may overlap with other update operations (including other puts and removes). Retrievals reflect the results of the most recently completed update operations holding upon their onset. For aggregate operations such as putAll, 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.

Very full tables, or tables with high reprobe rates may trigger an internal resize operation to move into a larger table. Resizing is not terribly expensive, but it is not free either; during resize operations table throughput may drop somewhat. All threads that visit the table during a resize will 'help' the resizing but will still be allowed to complete their operation before the resize is finished (i.e., a simple 'get' operation on a million-entry table undergoing resizing will not need to block until the entire million entries are copied).

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.

从以下版本开始:

1.5 Forked from JCTools.

作者:

Cliff Click

另请参阅:

序列化表格

嵌套类概要

从类继承的嵌套类/接口 java.util.AbstractMap

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

从接口继承的嵌套类/接口 java.util.Map

Map.Entry<K,V>

字段概要

字段

限定符和类型	字段和说明
static Object	TOMBSTONE

构造器概要

构造器

构造器和说明
NonBlockingHashMap() Create a new NonBlockingHashMap with default minimum size (currently set to 8 K/V pairs or roughly 84 bytes on a standard 32-bit JVM).
NonBlockingHashMap(int initial_sz) Create a new NonBlockingHashMap with initial room for the given number of elements, thus avoiding internal resizing operations to reach an appropriate size.

方法概要

方法

限定符和类型	方法和说明
void	clear() Removes all of the mappings from this map.
Object	clone() Creates a shallow copy of this hashtable.
boolean	contains(Object val) Legacy method testing if some key maps into the specified value in this table.
boolean	containsKey(Object key) Tests if the key in the table using the equals method.
boolean	containsValue(Object val) Returns true if this Map maps one or more keys to the specified value.
Enumeration<TypeV>	elements() Returns an enumeration of the values in this table.
Set<Map.Entry<TypeK,TypeV>>	entrySet() Returns a Set view of the mappings contained in this map.
TypeV	get(Object key) Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
TypeK	getk(TypeK key) Returns the Key to which the specified key is mapped, or null if this map contains no mapping for the key.
protected void	initialize()
boolean	isEmpty() Returns size() == 0.
Enumeration<TypeK>	keys() Returns an enumeration of the keys in this table.
Set<TypeK>	keySet() Returns a Set view of the keys contained in this map.
void	print() Verbose printout of table internals, useful for debugging.
TypeV	put(TypeK key, TypeV val) Maps the specified key to the specified value in the table.
void	putAll(Map<? extends TypeK,? extends TypeV> m) Copies all of the mappings from the specified map to this one, replacing any existing mappings.
TypeV	putIfAbsent(TypeK key, TypeV val) Atomically, do a put(TypeK, TypeV) if-and-only-if the key is not mapped.
TypeV	putIfMatchAllowNull(Object key, Object newVal, Object oldVal)
Object[]	raw_array()
protected void	rehash()
TypeV	remove(Object key) Removes the key (and its corresponding value) from this map.
boolean	remove(Object key, Object val) Atomically do a remove(Object) if-and-only-if the key is mapped to a value which is equals to the given value.
TypeV	replace(TypeK key, TypeV val) Atomically do a put(key,val) if-and-only-if the key is mapped to some value already.
boolean	replace(TypeK key, TypeV oldValue, TypeV newValue) Atomically do a put(key,newValue) if-and-only-if the key is mapped a value which is equals to oldValue.
long	reprobes() Get and clear the current count of reprobes.
int	size() Returns the number of key-value mappings in this map.
String	toString() Returns a string representation of this map.
Collection<TypeV>	values() Returns a Collection view of the values contained in this map.

从类继承的方法 java.util.AbstractMap

equals, hashCode

从类继承的方法 java.lang.Object

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

从接口继承的方法 java.util.Map

equals, hashCode

字段详细资料

TOMBSTONE

public static final Object TOMBSTONE

构造器详细资料

NonBlockingHashMap

public NonBlockingHashMap()

Create a new NonBlockingHashMap with default minimum size (currently set to 8 K/V pairs or roughly 84 bytes on a standard 32-bit JVM).

NonBlockingHashMap

public NonBlockingHashMap(int initial_sz)

Create a new NonBlockingHashMap with initial room for the given number of elements, thus avoiding internal resizing operations to reach an appropriate size. Large numbers here when used with a small count of elements will sacrifice space for a small amount of time gained. The initial size will be rounded up internally to the next larger power of 2.

方法详细资料

print

public final void print()

Verbose printout of table internals, useful for debugging.

reprobes

public long reprobes()

Get and clear the current count of reprobes. Reprobes happen on key collisions, and a high reprobe rate may indicate a poor hash function or weaknesses in the table resizing function.

返回:

the count of reprobes since the last call to reprobes() or since the table was created.

initialize

protected final void initialize()

size

public int size()

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

指定者:

size 在接口中 Map<TypeK,TypeV>

覆盖:

size 在类中 AbstractMap<TypeK,TypeV>

返回:

the number of key-value mappings in this map

isEmpty

public boolean isEmpty()

Returns size() == 0.

指定者:

isEmpty 在接口中 Map<TypeK,TypeV>

覆盖:

isEmpty 在类中 AbstractMap<TypeK,TypeV>

返回:

size() == 0

containsKey

public boolean containsKey(Object key)

Tests if the key in the table using the equals method.

指定者:

containsKey 在接口中 Map<TypeK,TypeV>

覆盖:

containsKey 在类中 AbstractMap<TypeK,TypeV>

返回:

true if the key is in the table using the equals method

抛出:

NullPointerException - if the specified key is null

contains

public boolean contains(Object val)

Legacy method testing if some key maps into the specified value in this table. This method is identical in functionality to 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.

参数:

val - a value to search for

返回:

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

抛出:

NullPointerException - if the specified value is null

put

public TypeV put(TypeK key,
        TypeV val)

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

The value can be retrieved by calling get(java.lang.Object) with a key that is equal to the original key.

指定者:

put 在接口中 Map<TypeK,TypeV>

覆盖:

put 在类中 AbstractMap<TypeK,TypeV>

参数:

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

val - value to be associated with the specified key

返回:

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

抛出:

NullPointerException - if the specified key or value is null

putIfAbsent

public TypeV putIfAbsent(TypeK key,
                TypeV val)

Atomically, do a put(TypeK, TypeV) if-and-only-if the key is not mapped. Useful to ensure that only a single mapping for the key exists, even if many threads are trying to create the mapping in parallel.

指定者:

putIfAbsent 在接口中 ConcurrentMap<TypeK,TypeV>

返回:

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

抛出:

NullPointerException - if the specified key or value is null

remove

public TypeV 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.

指定者:

remove 在接口中 Map<TypeK,TypeV>

覆盖:

remove 在类中 AbstractMap<TypeK,TypeV>

返回:

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

抛出:

NullPointerException - if the specified key is null

remove

public boolean remove(Object key,
             Object val)

Atomically do a remove(Object) if-and-only-if the key is mapped to a value which is equals to the given value.

指定者:

remove 在接口中 ConcurrentMap<TypeK,TypeV>

抛出:

NullPointerException - if the specified key or value is null

replace

public TypeV replace(TypeK key,
            TypeV val)

Atomically do a put(key,val) if-and-only-if the key is mapped to some value already.

指定者:

replace 在接口中 ConcurrentMap<TypeK,TypeV>

抛出:

NullPointerException - if the specified key or value is null

replace

public boolean replace(TypeK key,
              TypeV oldValue,
              TypeV newValue)

Atomically do a put(key,newValue) if-and-only-if the key is mapped a value which is equals to oldValue.

指定者:

replace 在接口中 ConcurrentMap<TypeK,TypeV>

抛出:

NullPointerException - if the specified key or value is null

putIfMatchAllowNull

public final TypeV putIfMatchAllowNull(Object key,
                        Object newVal,
                        Object oldVal)

putAll

public void putAll(Map<? extends TypeK,? extends TypeV> m)

Copies all of the mappings from the specified map to this one, replacing any existing mappings.

指定者:

putAll 在接口中 Map<TypeK,TypeV>

覆盖:

putAll 在类中 AbstractMap<TypeK,TypeV>

参数:

m - mappings to be stored in this map

clear

public void clear()

Removes all of the mappings from this map.

指定者:

clear 在接口中 Map<TypeK,TypeV>

覆盖:

clear 在类中 AbstractMap<TypeK,TypeV>

containsValue

public boolean containsValue(Object val)

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 is much slower than containsKey(java.lang.Object).

指定者:

containsValue 在接口中 Map<TypeK,TypeV>

覆盖:

containsValue 在类中 AbstractMap<TypeK,TypeV>

参数:

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

返回:

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

抛出:

NullPointerException - if the specified value is null

rehash

protected void rehash()

clone

public Object clone()

Creates a shallow copy of this hashtable. All the structure of the hashtable itself is copied, but the keys and values are not cloned. This is a relatively expensive operation.

覆盖:

clone 在类中 AbstractMap<TypeK,TypeV>

返回:

a clone of the hashtable.

toString

public String toString()

Returns a string representation of this map. The string representation consists of a list of key-value mappings in the order returned by the map's entrySet view's iterator, enclosed in braces ("{}"). Adjacent mappings are separated by the characters ", " (comma and space). Each key-value mapping is rendered as the key followed by an equals sign ("=") followed by the associated value. Keys and values are converted to strings as by String.valueOf(Object).

覆盖:

toString 在类中 AbstractMap<TypeK,TypeV>

返回:

a string representation of this map

get

public TypeV 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.)

指定者:

get 在接口中 Map<TypeK,TypeV>

覆盖:

get 在类中 AbstractMap<TypeK,TypeV>

抛出:

NullPointerException - if the specified key is null

getk

public TypeK getk(TypeK key)

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

抛出:

NullPointerException - if the specified key is null

raw_array

public Object[] raw_array()

elements

public Enumeration<TypeV> elements()

Returns an enumeration of the values in this table.

返回:

an enumeration of the values in this table

另请参阅:

values()

values

public Collection<TypeV> 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.

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.

指定者:

values 在接口中 Map<TypeK,TypeV>

覆盖:

values 在类中 AbstractMap<TypeK,TypeV>

keys

public Enumeration<TypeK> keys()

Returns an enumeration of the keys in this table.

返回:

an enumeration of the keys in this table

另请参阅:

keySet()

keySet

public Set<TypeK> 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.

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.

指定者:

keySet 在接口中 Map<TypeK,TypeV>

覆盖:

keySet 在类中 AbstractMap<TypeK,TypeV>

entrySet

public Set<Map.Entry<TypeK,TypeV>> entrySet()

Returns a 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.

Warning: the iterator associated with this Set requires the creation of Map.Entry objects with each iteration. The NonBlockingHashMap does not normally create or using Map.Entry objects so they will be created soley to support this iteration. Iterating using keySet() or values() will be more efficient.

指定者:

entrySet 在接口中 Map<TypeK,TypeV>

指定者:

entrySet 在类中 AbstractMap<TypeK,TypeV>