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Java Source Code / Java Documentation » Library » Apache beehive 1.0.2 src » org.apache.beehive.netui.util.internal.concurrent 
Source Cross Reference  Class Diagram Java Document (Java Doc) 


java.lang.Object
   java.util.AbstractMap
      org.apache.beehive.netui.util.internal.concurrent.InternalConcurrentHashMap

InternalConcurrentHashMap
public class InternalConcurrentHashMap extends AbstractMap implements Map,Serializable(Code)
A hash table supporting full concurrency of retrievals and adjustable expected concurrency for updates. This class obeys the same functional specification as java.util.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 java.util.Hashtable but unlike java.util.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.
since:
   1.5
author:
   Doug Lea


Inner Class :final static class HashEntry
Inner Class :final static class Segment extends ReentrantLock implements Serializable
Inner Class :abstract class HashIterator
Inner Class :final class KeyIterator extends HashIterator implements Iterator,Enumeration
Inner Class :final class ValueIterator extends HashIterator implements Iterator,Enumeration
Inner Class :final class EntryIterator extends HashIterator implements Map.Entry,Iterator
Inner Class :final class KeySet extends AbstractSet
Inner Class :final class Values extends AbstractCollection
Inner Class :final class EntrySet extends AbstractSet
Inner Class :final static class SimpleEntry implements Entry

Field Summary
static  intDEFAULT_INITIAL_CAPACITY
     The default initial number of table slots for this table.
final static  floatDEFAULT_LOAD_FACTOR
     The default load factor for this table.
final static  intDEFAULT_SEGMENTS
     The default number of concurrency control segments.
final static  intMAXIMUM_CAPACITY
     The maximum capacity, used if a higher value is implicitly specified by either of the constructors with arguments.
final static  intMAX_SEGMENTS
     The maximum number of segments to allow; used to bound constructor arguments.
final static  intRETRIES_BEFORE_LOCK
     Number of unsynchronized retries in size and containsValue methods before resorting to locking.
transient  SetentrySet
    
transient  SetkeySet
    
final  intsegmentMask
     Mask value for indexing into segments.
final  intsegmentShift
     Shift value for indexing within segments.
final  Segment[]segments
    
transient  Collectionvalues
    

Constructor Summary
public  InternalConcurrentHashMap(int initialCapacity, float loadFactor, int concurrencyLevel)
     Creates a new, empty map with the specified initial capacity and the specified load factor.
Parameters:
  initialCapacity - the initial capacity.
public  InternalConcurrentHashMap(int initialCapacity, float loadFactor)
     Creates a new, empty map with the specified initial Creates a new, empty map with the specified initial capacity and load factor and with the default concurrencyLevel (16).
public  InternalConcurrentHashMap(int initialCapacity)
     capacity, and with default load factor (0.75f) and concurrencyLevel (16).
public  InternalConcurrentHashMap()
     Creates a new, empty map with a default initial capacity (16), load factor (0.75f), and concurrencyLevel (16).
public  InternalConcurrentHashMap(Map t)
     Creates a new map with the same mappings as the given map.

Method Summary
public  voidclear()
     Removes all mappings from this map.
public  booleancontains(Object value)
     Legacy method testing if some key maps into the specified value in this table.
public  booleancontainsKey(Object key)
     Tests if the specified object is a key in this table.
Parameters:
  key - possible key.
public  booleancontainsValue(Object value)
     Returns true if this map maps one or more keys to the specified value.
public  Enumerationelements()
     Returns an enumeration of the values in this table.
public  SetentrySet()
     Returns a collection view of the mappings contained in this map.
public  Objectget(Object key)
     Returns the value to which the specified key is mapped in this table.
Parameters:
  key - a key in the table.
static  inthash(Object x)
     Returns a hash code for non-null Object x.
public  booleanisEmpty()
    
public  SetkeySet()
     Returns a set view of the keys contained in this map.
public  Enumerationkeys()
     Returns an enumeration of the keys in this table.
public  Objectput(Object key, Object value)
     Maps the specified key to the specified value in this table.
public  voidputAll(Map t)
     Copies all of the mappings from the specified map to this one.
public  ObjectputIfAbsent(Object key, Object value)
     If the specified key is not already associated with a value, associate it with the given value. This is equivalent to
 if (!map.containsKey(key))
 return map.put(key, value);
 else
 return map.get(key);
 
Except that the action is performed atomically.
Parameters:
  key - key with which the specified value is to be associated.
Parameters:
  value - value to be associated with the specified key.
public  Objectremove(Object key)
     Removes the key (and its corresponding value) from this table.
public  booleanremove(Object key, Object value)
     Remove entry for key only if currently mapped to given value. Acts as
 if (map.get(key).equals(value)) {
 map.remove(key);
 return true;
 } else return false;
 
except that the action is performed atomically.
Parameters:
  key - key with which the specified value is associated.
Parameters:
  value - value associated with the specified key.
public  booleanreplace(Object key, Object oldValue, Object newValue)
     Replace entry for key only if currently mapped to given value. Acts as
 if (map.get(key).equals(oldValue)) {
 map.put(key, newValue);
 return true;
 } else return false;
 
except that the action is performed atomically.
Parameters:
  key - key with which the specified value is associated.
Parameters:
  oldValue - value expected to be associated with the specified key.
Parameters:
  newValue - value to be associated with the specified key.
public  Objectreplace(Object key, Object value)
     Replace entry for key only if currently mapped to some value. Acts as
 if ((map.containsKey(key)) {
 return map.put(key, value);
 } else return null;
 
except that the action is performed atomically.
Parameters:
  key - key with which the specified value is associated.
Parameters:
  value - value to be associated with the specified key.
final  SegmentsegmentFor(int hash)
    
public  intsize()
    
public  Collectionvalues()
     Returns a collection view of the values contained in this map.

Field Detail
DEFAULT_INITIAL_CAPACITY
static int DEFAULT_INITIAL_CAPACITY(Code)
The default initial number of table slots for this table. Used when not otherwise specified in constructor.



DEFAULT_LOAD_FACTOR
final static float DEFAULT_LOAD_FACTOR(Code)
The default load factor for this table. Used when not otherwise specified in constructor.



DEFAULT_SEGMENTS
final static int DEFAULT_SEGMENTS(Code)
The default number of concurrency control segments.



MAXIMUM_CAPACITY
final static int MAXIMUM_CAPACITY(Code)
The maximum capacity, used if a higher value is implicitly specified by either of the constructors with arguments. MUST be a power of two <= 1<<30 to ensure that entries are indexible using ints.



MAX_SEGMENTS
final static int MAX_SEGMENTS(Code)
The maximum number of segments to allow; used to bound constructor arguments.



RETRIES_BEFORE_LOCK
final static int RETRIES_BEFORE_LOCK(Code)
Number of unsynchronized retries in size and containsValue methods before resorting to locking. This is used to avoid unbounded retries if tables undergo continuous modification which would make it impossible to obtain an accurate result.



entrySet
transient Set entrySet(Code)



keySet
transient Set keySet(Code)



segmentMask
final int segmentMask(Code)
Mask value for indexing into segments. The upper bits of a key's hash code are used to choose the segment.



segmentShift
final int segmentShift(Code)
Shift value for indexing within segments.



segments
final Segment[] segments(Code)
The segments, each of which is a specialized hash table



values
transient Collection values(Code)




Constructor Detail
InternalConcurrentHashMap
public InternalConcurrentHashMap(int initialCapacity, float loadFactor, int concurrencyLevel)(Code)
Creates a new, empty map with the specified initial capacity and the specified load factor.
Parameters:
  initialCapacity - the initial capacity. The implementationperforms internal sizing to accommodate this many elements.
Parameters:
  loadFactor - the load factor threshold, used to control resizing.
Parameters:
  concurrencyLevel - the estimated number of concurrentlyupdating threads. The implementation performs internal sizingto try to accommodate this many threads.
throws:
  IllegalArgumentException - if the initial capacity isnegative or the load factor or concurrencyLevel arenonpositive.



InternalConcurrentHashMap
public InternalConcurrentHashMap(int initialCapacity, float loadFactor)(Code)
Creates a new, empty map with the specified initial Creates a new, empty map with the specified initial capacity and load factor and with the default concurrencyLevel (16).
Parameters:
  initialCapacity - The implementation performs internalsizing to accommodate this many elements.
Parameters:
  loadFactor - the load factor threshold, used to control resizing.
throws:
  IllegalArgumentException - if the initial capacity ofelements is negative or the load factor is nonpositive



InternalConcurrentHashMap
public InternalConcurrentHashMap(int initialCapacity)(Code)
capacity, and with default load factor (0.75f) and concurrencyLevel (16).
Parameters:
  initialCapacity - The implementation performs internalsizing to accommodate this many elements.
throws:
  IllegalArgumentException - if the initial capacity ofelements is negative.



InternalConcurrentHashMap
public InternalConcurrentHashMap()(Code)
Creates a new, empty map with a default initial capacity (16), load factor (0.75f), and concurrencyLevel (16).



InternalConcurrentHashMap
public InternalConcurrentHashMap(Map t)(Code)
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 (0.75f) and concurrencyLevel(16).
Parameters:
  t - the map




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



contains
public boolean contains(Object value)(Code)
Legacy method testing if some key maps into the specified value in this table. This method is identical in functionality to InternalConcurrentHashMap.containsValue , and exists solely to ensure full compatibility with class java.util.Hashtable , which supported this method prior to introduction of the Java Collections framework.
Parameters:
  value - a value to search for. true if and only if some key maps to thevalue argument in this table asdetermined by the equals method;false otherwise.
throws:
  NullPointerException - if the value is null.



containsKey
public boolean containsKey(Object key)(Code)
Tests if the specified object is a key in this table.
Parameters:
  key - possible key. true if and only if the specified objectis a key in this table, as determined by theequals method; false otherwise.
throws:
  NullPointerException - if the key isnull.



containsValue
public boolean containsValue(Object value)(Code)
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.
Parameters:
  value - value whose presence in this map is to be tested. true if this map maps one or more keys to thespecified value.
throws:
  NullPointerException - if the value is null.



elements
public Enumeration elements()(Code)
Returns an enumeration of the values in this table. an enumeration of the values in this table.
See Also:   InternalConcurrentHashMap.values



entrySet
public Set entrySet()(Code)
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. The view's returned iterator is a "weakly consistent" iterator that will never throw java.util.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. a collection view of the mappings contained in this map.



get
public Object get(Object key)(Code)
Returns the value to which the specified key is mapped in this table.
Parameters:
  key - a key in the table. the value to which the key is mapped in this table;null if the key is not mapped to any value inthis table.
throws:
  NullPointerException - if the key isnull.



hash
static int hash(Object x)(Code)
Returns a hash code for non-null Object x. Uses the same hash code spreader as most other java.util hash tables.
Parameters:
  x - the object serving as a key the hash code



isEmpty
public boolean isEmpty()(Code)



keySet
public Set keySet()(Code)
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 returned iterator is a "weakly consistent" iterator that will never throw java.util.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. a set view of the keys contained in this map.



keys
public Enumeration keys()(Code)
Returns an enumeration of the keys in this table. an enumeration of the keys in this table.
See Also:   InternalConcurrentHashMap.keySet



put
public Object put(Object key, Object value)(Code)
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.
Parameters:
  key - the table key.
Parameters:
  value - the value. the previous value of the specified key in this table,or null if it did not have one.
throws:
  NullPointerException - if the key or value isnull.




putAll
public void putAll(Map t)(Code)
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.



putIfAbsent
public Object putIfAbsent(Object key, Object value)(Code)
If the specified key is not already associated with a value, associate it with the given value. This is equivalent to
 if (!map.containsKey(key))
 return map.put(key, value);
 else
 return map.get(key);
 
Except that the action is performed atomically.
Parameters:
  key - key with which the specified value is to be associated.
Parameters:
  value - value to be associated with the specified key. previous value associated with specified key, or nullif there was no mapping for key.
throws:
  NullPointerException - if the specified key or value isnull.



remove
public Object remove(Object key)(Code)
Removes the key (and its corresponding value) from this table. This method does nothing if the key is not in the table.
Parameters:
  key - the key that needs to be removed. the value to which the key had been mapped in this table,or null if the key did not have a mapping.
throws:
  NullPointerException - if the key isnull.



remove
public boolean remove(Object key, Object value)(Code)
Remove entry for key only if currently mapped to given value. Acts as
 if (map.get(key).equals(value)) {
 map.remove(key);
 return true;
 } else return false;
 
except that the action is performed atomically.
Parameters:
  key - key with which the specified value is associated.
Parameters:
  value - value associated with the specified key. true if the value was removed
throws:
  NullPointerException - if the specified key isnull.



replace
public boolean replace(Object key, Object oldValue, Object newValue)(Code)
Replace entry for key only if currently mapped to given value. Acts as
 if (map.get(key).equals(oldValue)) {
 map.put(key, newValue);
 return true;
 } else return false;
 
except that the action is performed atomically.
Parameters:
  key - key with which the specified value is associated.
Parameters:
  oldValue - value expected to be associated with the specified key.
Parameters:
  newValue - value to be associated with the specified key. true if the value was replaced
throws:
  NullPointerException - if the specified key or values arenull.



replace
public Object replace(Object key, Object value)(Code)
Replace entry for key only if currently mapped to some value. Acts as
 if ((map.containsKey(key)) {
 return map.put(key, value);
 } else return null;
 
except that the action is performed atomically.
Parameters:
  key - key with which the specified value is associated.
Parameters:
  value - value to be associated with the specified key. previous value associated with specified key, or nullif there was no mapping for key.
throws:
  NullPointerException - if the specified key or value isnull.



segmentFor
final Segment segmentFor(int hash)(Code)
Returns the segment that should be used for key with given hash
Parameters:
  hash - the hash code for the key the segment



size
public int size()(Code)



values
public Collection values()(Code)
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 returned iterator is a "weakly consistent" iterator that will never throw java.util.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. a collection view of the values contained in this map.



Methods inherited from java.util.AbstractMap
public void clear()(Code)(Java Doc)
protected Object clone() throws CloneNotSupportedException(Code)(Java Doc)
public boolean containsKey(Object key)(Code)(Java Doc)
public boolean containsValue(Object value)(Code)(Java Doc)
abstract public Set<Entry<K, V>> entrySet()(Code)(Java Doc)
public boolean equals(Object o)(Code)(Java Doc)
public V get(Object key)(Code)(Java Doc)
public int hashCode()(Code)(Java Doc)
public boolean isEmpty()(Code)(Java Doc)
public Set<K> keySet()(Code)(Java Doc)
public V put(K key, V value)(Code)(Java Doc)
public void putAll(Map<? extends K, ? extends V> m)(Code)(Java Doc)
public V remove(Object key)(Code)(Java Doc)
public int size()(Code)(Java Doc)
public String toString()(Code)(Java Doc)
public Collection<V> values()(Code)(Java Doc)

Methods inherited from java.lang.Object
native protected Object clone() throws CloneNotSupportedException(Code)(Java Doc)
public boolean equals(Object obj)(Code)(Java Doc)
protected void finalize() throws Throwable(Code)(Java Doc)
final native public Class getClass()(Code)(Java Doc)
native public int hashCode()(Code)(Java Doc)
final native public void notify()(Code)(Java Doc)
final native public void notifyAll()(Code)(Java Doc)
public String toString()(Code)(Java Doc)
final native public void wait(long timeout) throws InterruptedException(Code)(Java Doc)
final public void wait(long timeout, int nanos) throws InterruptedException(Code)(Java Doc)
final public void wait() throws InterruptedException(Code)(Java Doc)

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