java.util.concurrent
Class ConcurrentHashMap.Segment<K,V>

java.lang.Object
  java.util.concurrent.locks.ReentrantLock
      java.util.concurrent.ConcurrentHashMap.Segment<K,V>

All Implemented Interfaces:

Serializable, Lock

Enclosing class:

ConcurrentHashMap<K,V>

static final class ConcurrentHashMap.Segment<K,V>
extends ReentrantLock
implements Serializable

Segments are specialized versions of hash tables. This subclasses from ReentrantLock opportunistically, just to simplify some locking and avoid separate construction.

Field Summary

(package private) int	count The number of elements in this segment's region.
(package private) float	loadFactor The load factor for the hash table.
(package private) int	modCount Number of updates; used for checking lack of modifications in bulk-read methods.
(package private) ConcurrentHashMap.HashEntry[]	table The per-segment table
(package private) int	threshold The table is rehashed when its size exceeds this threshold.

Constructor Summary

ConcurrentHashMap.Segment(int initialCapacity, float lf)

Method Summary

(package private) void	clear()
(package private) boolean	containsKey(Object key, int hash)
(package private) boolean	containsValue(Object value)
(package private) V	get(Object key, int hash)
(package private) V	put(K key, int hash, V value, boolean onlyIfAbsent)
(package private) ConcurrentHashMap.HashEntry[]	rehash(ConcurrentHashMap.HashEntry[] oldTable)
(package private) V	remove(Object key, int hash, Object value) Remove; match on key only if value null, else match both.
(package private) V	replace(K key, int hash, V newValue)
(package private) boolean	replace(K key, int hash, V oldValue, V newValue)
(package private) void	setTable(ConcurrentHashMap.HashEntry[] newTable) Set table to new HashEntry array.

Methods inherited from class java.util.concurrent.locks.ReentrantLock

getHoldCount, getOwner, getQueuedThreads, getQueueLength, getWaitingThreads, getWaitQueueLength, hasQueuedThread, hasQueuedThreads, hasWaiters, isFair, isHeldByCurrentThread, isLocked, lock, lockInterruptibly, newCondition, toString, tryLock, tryLock, unlock

Methods inherited from class java.lang.Object

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

Field Detail

count

transient volatile int count

The number of elements in this segment's region.

modCount

transient int modCount

Number of updates; used for checking lack of modifications in bulk-read methods.

threshold

transient int threshold

The table is rehashed when its size exceeds this threshold. (The value of this field is always (int)(capacity * loadFactor).)

table

transient ConcurrentHashMap.HashEntry[] table

The per-segment table

loadFactor

final float loadFactor

The load factor for the hash table. Even though this value is same for all segments, it is replicated to avoid needing links to outer object.

Constructor Detail

ConcurrentHashMap.Segment

ConcurrentHashMap.Segment(int initialCapacity,
                          float lf)

Method Detail

setTable

void setTable(ConcurrentHashMap.HashEntry[] newTable)

Set table to new HashEntry array. Call only while holding lock or in constructor.

get

V get(Object key,
      int hash)

containsKey

boolean containsKey(Object key,
                    int hash)

containsValue

boolean containsValue(Object value)

replace

boolean replace(K key,
                int hash,
                V oldValue,
                V newValue)

replace

V replace(K key,
          int hash,
          V newValue)

put

V put(K key,
      int hash,
      V value,
      boolean onlyIfAbsent)

rehash

ConcurrentHashMap.HashEntry[] rehash(ConcurrentHashMap.HashEntry[] oldTable)

remove

V remove(Object key,
         int hash,
         Object value)

Remove; match on key only if value null, else match both.

clear

void clear()