TypeV - the type of mapped valuespublic class NonBlockingHashMapLong<TypeV> extends AbstractMap<Long,TypeV> implements ConcurrentMap<Long,TypeV>, Serializable
ConcurrentHashMap
with primitive long keys, better scaling properties and
generally lower costs. The use of long keys allows for faster
compares and lower memory costs. The Map provides identical correctness
properties as ConcurrentHashMap. All operations are non-blocking and
multi-thread safe, including all update operations. NonBlockingHashMapLong scales substatially 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 Niagra box, 8-way Intel box and a 4-way Power box.
The main benefit of this class over using plain NonBlockingHashMap with Long keys is
that it avoids the auto-boxing and unboxing costs. Since auto-boxing is
automatic, it is easy to accidentally cause auto-boxing and negate
the space and speed benefits.
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 value.
| Modifier and Type | Class and Description |
|---|---|
class |
NonBlockingHashMapLong.IteratorLong
A class which implements the
Iterator and Enumeration
interfaces, generified to the Long class and supporting a
non-auto-boxing NonBlockingHashMapLong.IteratorLong.nextLong() function. |
AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>| Constructor and Description |
|---|
NonBlockingHashMapLong()
Create a new NonBlockingHashMapLong with default minimum size (currently set
to 8 K/V pairs or roughly 84 bytes on a standard 32-bit JVM).
|
NonBlockingHashMapLong(boolean opt_for_space)
Create a new NonBlockingHashMapLong, setting the space-for-speed
tradeoff.
|
NonBlockingHashMapLong(int initial_sz)
Create a new NonBlockingHashMapLong with initial room for the given
number of elements, thus avoiding internal resizing operations to reach
an appropriate size.
|
NonBlockingHashMapLong(int initial_sz,
boolean opt_for_space)
Create a new NonBlockingHashMapLong, setting both the initial size and
the space-for-speed tradeoff.
|
| Modifier and Type | Method and Description |
|---|---|
void |
clear()
Removes all of the mappings from this map.
|
boolean |
contains(Object val)
Legacy method testing if some key maps into the specified value in this
table.
|
boolean |
containsKey(long key)
Tests if the key in the table.
|
boolean |
containsKey(Object key)
Auto-boxing version of
containsKey(long). |
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<Long,TypeV>> |
entrySet()
Returns a
Set view of the mappings contained in this map. |
TypeV |
get(long key)
Returns the value to which the specified key is mapped, or
null
if this map contains no mapping for the key. |
TypeV |
get(Object key)
Auto-boxing version of
get(long). |
Enumeration<Long> |
keys()
Returns an enumeration of the auto-boxed keys in this table.
|
Set<Long> |
keySet()
Returns a
Set view of the keys contained in this map; with care
the keys may be iterated over without auto-boxing. |
long[] |
keySetLong()
Keys as a long array.
|
void |
print()
Verbose printout of table internals, useful for debugging.
|
TypeV |
put(long key,
TypeV val)
Maps the specified key to the specified value in the table.
|
TypeV |
put(Long key,
TypeV val)
Auto-boxing version of
put(long, TypeV). |
TypeV |
putIfAbsent(long key,
TypeV val)
Atomically, do a
put(long, TypeV) if-and-only-if the key is not mapped. |
TypeV |
putIfAbsent(Long key,
TypeV val)
Auto-boxing version of
putIfAbsent(long, TypeV). |
TypeV |
remove(long key)
Removes the key (and its corresponding value) from this map.
|
boolean |
remove(long key,
Object val)
Atomically do a
remove(long) if-and-only-if the key is mapped
to a value which is equals to the given value. |
TypeV |
remove(Object key)
Auto-boxing version of
remove(long). |
boolean |
remove(Object key,
Object Val)
Auto-boxing version of
remove(long,Object). |
TypeV |
replace(long key,
TypeV val)
Atomically do a
put(key,val) if-and-only-if the key is
mapped to some value already. |
TypeV |
replace(Long key,
TypeV Val)
Auto-boxing version of
replace(long, TypeV). |
boolean |
replace(long 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. |
boolean |
replace(Long key,
TypeV oldValue,
TypeV newValue)
Auto-boxing version of
replace(long, TypeV). |
int |
size()
Returns the number of key-value mappings in this map.
|
Collection<TypeV> |
values()
Returns a
Collection view of the values contained in this map. |
clone, equals, hashCode, isEmpty, putAll, toStringfinalize, getClass, notify, notifyAll, wait, wait, waitcompute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, replaceAllpublic NonBlockingHashMapLong()
public NonBlockingHashMapLong(int initial_sz)
public NonBlockingHashMapLong(boolean opt_for_space)
true optimizes for space and is the default. false optimizes for speed and doubles space costs for roughly a 10%
speed improvement.public NonBlockingHashMapLong(int initial_sz,
boolean opt_for_space)
true optimizes for space and is
the default. false optimizes for speed and doubles space costs
for roughly a 10% speed improvement.public final void print()
public int size()
public boolean containsKey(long key)
public boolean contains(Object val)
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.val - a value to search forNullPointerException - if the specified value is nullpublic TypeV put(long key, TypeV val)
The value can be retrieved by calling get(long)
with a key that is equal to the original key.
key - key with which the specified value is to be associatedval - value to be associated with the specified keyNullPointerException - if the specified value is nullpublic TypeV putIfAbsent(long key, TypeV val)
put(long, 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.NullPointerException - if the specified is value is nullpublic TypeV remove(long key)
public boolean remove(long key,
Object val)
remove(long) if-and-only-if the key is mapped
to a value which is equals to the given value.NullPointerException - if the specified value is nullpublic TypeV replace(long key, TypeV val)
put(key,val) if-and-only-if the key is
mapped to some value already.NullPointerException - if the specified value is nullpublic boolean replace(long key,
TypeV oldValue,
TypeV newValue)
put(key,newValue) if-and-only-if the key is
mapped a value which is equals to oldValue.NullPointerException - if the specified value is nullpublic void clear()
public boolean containsValue(Object val)
containsKey(long).containsValue in interface Map<Long,TypeV>containsValue in class AbstractMap<Long,TypeV>val - value whose presence in this map is to be testedNullPointerException - if the specified value is nullpublic final TypeV get(long 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==k, then this method
returns v; otherwise it returns null. (There can be at
most one such mapping.)
NullPointerException - if the specified key is nullpublic TypeV remove(Object key)
remove(long).public boolean remove(Object key, Object Val)
remove(long,Object).public boolean containsKey(Object key)
containsKey(long).containsKey in interface Map<Long,TypeV>containsKey in class AbstractMap<Long,TypeV>public TypeV putIfAbsent(Long key, TypeV val)
putIfAbsent(long, TypeV).putIfAbsent in interface ConcurrentMap<Long,TypeV>putIfAbsent in interface Map<Long,TypeV>public TypeV replace(Long key, TypeV Val)
replace(long, TypeV).public TypeV put(Long key, TypeV val)
put(long, TypeV).public boolean replace(Long key, TypeV oldValue, TypeV newValue)
replace(long, TypeV).public Enumeration<TypeV> elements()
values()public Collection<TypeV> 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 Enumeration<Long> keys()
keySet()public Set<Long> keySet()
Set view of the keys contained in this map; with care
the keys may be iterated over without auto-boxing. 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 long[] keySetLong()
public Set<Map.Entry<Long,TypeV>> 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.
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. In addition,
this version requires auto-boxing the keys.
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