org.mapdb

Class LongConcurrentHashMap<V>

java.lang.Object

org.mapdb.LongMap<V>

org.mapdb.LongConcurrentHashMap<V>

All Implemented Interfaces:

java.io.Serializable

public class LongConcurrentHashMap<V>
extends LongMap<V>
implements java.io.Serializable

Thread safe LongMap. Is refactored version of 'ConcurrentHashMap'

Author:

Jan Kotek, Doug Lea

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
(package private) static class	LongConcurrentHashMap.HashEntry<V> LongConcurrentHashMap list entry.
(package private) class	LongConcurrentHashMap.HashIterator
(package private) class	LongConcurrentHashMap.KeyIterator
(package private) class	LongConcurrentHashMap.MapIterator
(package private) static class	LongConcurrentHashMap.Segment<V> Segments are specialized versions of hash tables.
(package private) class	LongConcurrentHashMap.ValueIterator

Nested classes/interfaces inherited from class org.mapdb.LongMap

LongMap.LongMapIterator<V>

Field Summary

Fields

Modifier and Type	Field and Description
(package private) static int	DEFAULT_CONCURRENCY_LEVEL The default concurrency level for this table, used when not otherwise specified in a constructor.
(package private) static int	DEFAULT_INITIAL_CAPACITY The default initial capacity for this table, used when not otherwise specified in a constructor.
(package private) static float	DEFAULT_LOAD_FACTOR The default load factor for this table, used when not otherwise specified in a constructor.
protected long	hashSalt Salt added to keys before hashing, so it is harder to trigger hash collision attack.
(package private) static int	MAX_SEGMENTS The maximum number of segments to allow; used to bound constructor arguments.
(package private) static int	MAXIMUM_CAPACITY The maximum capacity, used if a higher value is implicitly specified by either of the constructors with arguments.
(package private) static int	RETRIES_BEFORE_LOCK Number of unsynchronized retries in size and containsValue methods before resorting to locking.
(package private) int	segmentMask Mask value for indexing into segments.
(package private) LongConcurrentHashMap.Segment<V>[]	segments The segments, each of which is a specialized hash table
(package private) int	segmentShift Shift value for indexing within segments.
private static long	serialVersionUID

Constructor Summary

Constructors

Constructor and Description
LongConcurrentHashMap() Creates a new, empty map with a default initial capacity (16), load factor (0.75) and concurrencyLevel (16).
LongConcurrentHashMap(int initialCapacity) Creates a new, empty map with the specified initial capacity, and with default load factor (0.75) and concurrencyLevel (16).
LongConcurrentHashMap(int initialCapacity, float loadFactor, int concurrencyLevel) Creates a new, empty map with the specified initial capacity, load factor and concurrency level.

Method Summary

Modifier and Type	Method and Description
void	clear() Removes all of the mappings from this map.
boolean	containsKey(long key) Tests if the specified object is a key in this table.
boolean	containsValue(java.lang.Object value) Returns true if this map maps one or more keys to the specified value.
V	get(long 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.
LongMap.LongMapIterator<V>	longMapIterator()
V	put(long key, V value) Maps the specified key to the specified value in this table.
V	putIfAbsent(long key, V value)
V	remove(long key) Removes the key (and its corresponding value) from this map.
boolean	remove(long key, java.lang.Object value)
V	replace(long key, V value)
boolean	replace(long key, V oldValue, V newValue)
(package private) LongConcurrentHashMap.Segment<V>	segmentFor(int hash) Returns the segment that should be used for key with given hash
int	size() Returns the number of key-value mappings in this map.
java.util.Iterator<V>	valuesIterator()

Methods inherited from class org.mapdb.LongMap

toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

serialVersionUID

private static final long serialVersionUID

See Also:

Constant Field Values

DEFAULT_INITIAL_CAPACITY

static final int DEFAULT_INITIAL_CAPACITY

The default initial capacity for this table, used when not otherwise specified in a constructor.

See Also:

Constant Field Values

hashSalt

protected final long hashSalt

Salt added to keys before hashing, so it is harder to trigger hash collision attack.

DEFAULT_LOAD_FACTOR

static final float DEFAULT_LOAD_FACTOR

The default load factor for this table, used when not otherwise specified in a constructor.

See Also:

Constant Field Values

DEFAULT_CONCURRENCY_LEVEL

static final int DEFAULT_CONCURRENCY_LEVEL

The default concurrency level for this table, used when not otherwise specified in a constructor.

See Also:

Constant Field Values

MAXIMUM_CAPACITY

static final int MAXIMUM_CAPACITY

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 indexable using ints.

See Also:

Constant Field Values

MAX_SEGMENTS

static final int MAX_SEGMENTS

The maximum number of segments to allow; used to bound constructor arguments.

See Also:

Constant Field Values

RETRIES_BEFORE_LOCK

static final int RETRIES_BEFORE_LOCK

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.

See Also:

Constant Field Values

segmentMask

final int segmentMask

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

Shift value for indexing within segments.

segments

final LongConcurrentHashMap.Segment<V>[] segments

The segments, each of which is a specialized hash table

Constructor Detail

LongConcurrentHashMap

public LongConcurrentHashMap(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:

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

LongConcurrentHashMap

public LongConcurrentHashMap(int initialCapacity)

Creates a new, empty map with the specified initial capacity, and with default load factor (0.75) and concurrencyLevel (16).

Parameters:

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

Throws:

java.lang.IllegalArgumentException - if the initial capacity of elements is negative.

LongConcurrentHashMap

public LongConcurrentHashMap()

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

Method Detail

segmentFor

final LongConcurrentHashMap.Segment<V> segmentFor(int hash)

Returns the segment that should be used for key with given hash

Parameters:

hash - the hash code for the key

Returns:

the segment

isEmpty

public boolean isEmpty()

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

Specified by:

isEmpty in class LongMap<V>

Returns:

true if this map contains no key-value mappings

See Also:

LongMap.size()

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 class LongMap<V>

Returns:

the number of key-value mappings in this map

valuesIterator

public java.util.Iterator<V> valuesIterator()

Specified by:

valuesIterator in class LongMap<V>

Returns:

iterator over values in map

longMapIterator

public LongMap.LongMapIterator<V> longMapIterator()

Specified by:

longMapIterator in class LongMap<V>

get

public V get(long 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 keys such that key.equals(k), then this method returns keys; otherwise it returns null. (There can be at most one such mapping.)

Specified by:

get in class LongMap<V>

Parameters:

key - the key.

Returns:

the value of the mapping with the specified key, or null if no mapping for the specified key is found.

Throws:

java.lang.NullPointerException - if the specified key is null

containsKey

public boolean containsKey(long key)

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

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:

java.lang.NullPointerException - if the specified key is null

containsValue

public boolean containsValue(java.lang.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.

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:

java.lang.NullPointerException - if the specified value is null

put

public V put(long 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 class LongMap<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:

java.lang.NullPointerException - if the specified key or value is null

putIfAbsent

public V putIfAbsent(long key,
                     V value)

Returns:

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

Throws:

java.lang.NullPointerException - if the specified key or value is null

remove

public V remove(long 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 class LongMap<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:

java.lang.NullPointerException - if the specified key is null

remove

public boolean remove(long key,
                      java.lang.Object value)

Throws:

java.lang.NullPointerException - if the specified key is null

replace

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

Throws:

java.lang.NullPointerException - if any of the arguments are null

replace

public V replace(long key,
                 V value)

Returns:

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

Throws:

java.lang.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 class LongMap<V>

See Also:

LongMap.isEmpty(), LongMap.size()