Package org.glassfish.jersey.internal.util.collection

Class ConcurrentHashMapV8<K,V>

java.lang.Object
java.util.AbstractMap<K,V>
org.glassfish.jersey.internal.util.collection.ConcurrentHashMapV8<K,V>
Type Parameters:
K - the type of keys maintained by this map
V - the type of mapped values
All Implemented Interfaces:
Serializable, ConcurrentMap<K,V>, Map<K,V>
class ConcurrentHashMapV8<K,V> extends AbstractMap<K,V> implements ConcurrentMap<K,V>, Serializable
A hash table supporting full concurrency of retrievals and high expected concurrency for updates. 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, 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. (More formally, an update operation for a given key bears a happens-before relation with any (non-null) retrieval for that key reporting the updated value.) 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. Bear in mind that the results of aggregate status methods including size, isEmpty, and containsValue are typically useful only when a map is not undergoing concurrent updates in other threads. Otherwise the results of these methods reflect transient states that may be adequate for monitoring or estimation purposes, but not for program control.

The table is dynamically expanded when there are too many collisions (i.e., keys that have distinct hash codes but fall into the same slot modulo the table size), with the expected average effect of maintaining roughly two bins per mapping (corresponding to a 0.75 load factor threshold for resizing). There may be much variance around this average as mappings are added and removed, but overall, this maintains a commonly accepted time/space tradeoff for hash tables. However, resizing this or any other kind of hash table may be a relatively slow operation. When possible, it is a good idea to provide a size estimate as an optional initialCapacity constructor argument. An additional optional loadFactor constructor argument provides a further means of customizing initial table capacity by specifying the table density to be used in calculating the amount of space to allocate for the given number of elements. Also, for compatibility with previous versions of this class, constructors may optionally specify an expected concurrencyLevel as an additional hint for internal sizing. Note that using many keys with exactly the same hashCode() is a sure way to slow down performance of any hash table. To ameliorate impact, when keys are Comparable, this class may use comparison order among keys to help break ties.

A Set projection of a ConcurrentHashMapV8 may be created (using newKeySet() or newKeySet(int)), or viewed (using keySet(Object) when only keys are of interest, and the mapped values are (perhaps transiently) not used or all take the same mapping value.

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.

ConcurrentHashMapV8s support a set of sequential and parallel bulk operations that are designed to be safely, and often sensibly, applied even with maps that are being concurrently updated by other threads; for example, when computing a snapshot summary of the values in a shared registry. There are three kinds of operation, each with four forms, accepting functions with Keys, Values, Entries, and (Key, Value) arguments and/or return values. Because the elements of a ConcurrentHashMapV8 are not ordered in any particular way, and may be processed in different orders in different parallel executions, the correctness of supplied functions should not depend on any ordering, or on any other objects or values that may transiently change while computation is in progress; and except for forEach actions, should ideally be side-effect-free. Bulk operations on Map.Entry objects do not support method setValue.

  • forEach: Perform a given action on each element. A variant form applies a given transformation on each element before performing the action.
  • search: Return the first available non-null result of applying a given function on each element; skipping further search when a result is found.
  • reduce: Accumulate each element. The supplied reduction function cannot rely on ordering (more formally, it should be both associative and commutative). There are five variants:
    • Plain reductions. (There is not a form of this method for (key, value) function arguments since there is no corresponding return type.)
    • Mapped reductions that accumulate the results of a given function applied to each element.
    • Reductions to scalar doubles, longs, and ints, using a given basis value.

These bulk operations accept a parallelismThreshold argument. Methods proceed sequentially if the current map size is estimated to be less than the given threshold. Using a value of Long.MAX_VALUE suppresses all parallelism. Using a value of 1 results in maximal parallelism by partitioning into enough subtasks to fully utilize the ForkJoinPool#commonPool() that is used for all parallel computations. Normally, you would initially choose one of these extreme values, and then measure performance of using in-between values that trade off overhead versus throughput.

The concurrency properties of bulk operations follow from those of ConcurrentHashMapV8: Any non-null result returned from get(key) and related access methods bears a happens-before relation with the associated insertion or update. The result of any bulk operation reflects the composition of these per-element relations (but is not necessarily atomic with respect to the map as a whole unless it is somehow known to be quiescent). Conversely, because keys and values in the map are never null, null serves as a reliable atomic indicator of the current lack of any result. To maintain this property, null serves as an implicit basis for all non-scalar reduction operations. For the double, long, and int versions, the basis should be one that, when combined with any other value, returns that other value (more formally, it should be the identity element for the reduction). Most common reductions have these properties; for example, computing a sum with basis 0 or a minimum with basis MAX_VALUE.

Search and transformation functions provided as arguments should similarly return null to indicate the lack of any result (in which case it is not used). In the case of mapped reductions, this also enables transformations to serve as filters, returning null (or, in the case of primitive specializations, the identity basis) if the element should not be combined. You can create compound transformations and filterings by composing them yourself under this "null means there is nothing there now" rule before using them in search or reduce operations.

Methods accepting and/or returning Entry arguments maintain key-value associations. They may be useful for example when finding the key for the greatest value. Note that "plain" Entry arguments can be supplied using new AbstractMap.SimpleEntry(k,v).

Bulk operations may complete abruptly, throwing an exception encountered in the application of a supplied function. Bear in mind when handling such exceptions that other concurrently executing functions could also have thrown exceptions, or would have done so if the first exception had not occurred.

Speedups for parallel compared to sequential forms are common but not guaranteed. Parallel operations involving brief functions on small maps may execute more slowly than sequential forms if the underlying work to parallelize the computation is more expensive than the computation itself. Similarly, parallelization may not lead to much actual parallelism if all processors are busy performing unrelated tasks.

All arguments to all task methods must be non-null.

jsr166e note: During transition, this class uses nested functional interfaces with different names but the same forms as those expected for JDK8.

This class is a member of the Java Collections Framework.

  • Field Details

    • serialVersionUID

      private static final long serialVersionUID
      See Also:

    • MAXIMUM_CAPACITY

      private static final int MAXIMUM_CAPACITY
      The largest possible table capacity. This value must be exactly 1invalid input: '<'invalid input: '<'30 to stay within Java array allocation and indexing bounds for power of two table sizes, and is further required because the top two bits of 32bit hash fields are used for control purposes.
      See Also:

    • DEFAULT_CAPACITY

      private static final int DEFAULT_CAPACITY
      The default initial table capacity. Must be a power of 2 (i.e., at least 1) and at most MAXIMUM_CAPACITY.
      See Also:

    • MAX_ARRAY_SIZE

      static final int MAX_ARRAY_SIZE
      The largest possible (non-power of two) array size. Needed by toArray and related methods.
      See Also:

    • DEFAULT_CONCURRENCY_LEVEL

      private static final int DEFAULT_CONCURRENCY_LEVEL
      The default concurrency level for this table. Unused but defined for compatibility with previous versions of this class.
      See Also:

    • LOAD_FACTOR

      private static final float LOAD_FACTOR
      The load factor for this table. Overrides of this value in constructors affect only the initial table capacity. The actual floating point value isn't normally used -- it is simpler to use expressions such as n - (n >>> 2) for the associated resizing threshold.
      See Also:

    • TREEIFY_THRESHOLD

      static final int TREEIFY_THRESHOLD
      The bin count threshold for using a tree rather than list for a bin. Bins are converted to trees when adding an element to a bin with at least this many nodes. The value must be greater than 2, and should be at least 8 to mesh with assumptions in tree removal about conversion back to plain bins upon shrinkage.
      See Also:

    • UNTREEIFY_THRESHOLD

      static final int UNTREEIFY_THRESHOLD
      The bin count threshold for untreeifying a (split) bin during a resize operation. Should be less than TREEIFY_THRESHOLD, and at most 6 to mesh with shrinkage detection under removal.
      See Also:

    • MIN_TREEIFY_CAPACITY

      static final int MIN_TREEIFY_CAPACITY
      The smallest table capacity for which bins may be treeified. (Otherwise the table is resized if too many nodes in a bin.) The value should be at least 4 * TREEIFY_THRESHOLD to avoid conflicts between resizing and treeification thresholds.
      See Also:

    • MIN_TRANSFER_STRIDE

      private static final int MIN_TRANSFER_STRIDE
      Minimum number of rebinnings per transfer step. Ranges are subdivided to allow multiple resizer threads. This value serves as a lower bound to avoid resizers encountering excessive memory contention. The value should be at least DEFAULT_CAPACITY.
      See Also:

    • MOVED

      static final int MOVED
      See Also:

    • TREEBIN

      static final int TREEBIN
      See Also:

    • RESERVED

      static final int RESERVED
      See Also:

    • HASH_BITS

      static final int HASH_BITS
      See Also:

    • NCPU

      static final int NCPU
      Number of CPUS, to place bounds on some sizings

    • serialPersistentFields

      private static final ObjectStreamField[] serialPersistentFields
      For serialization compatibility.

    • table

      transient volatile ConcurrentHashMapV8.Node<K,V>[] table
      The array of bins. Lazily initialized upon first insertion. Size is always a power of two. Accessed directly by iterators.

    • nextTable

      private transient volatile ConcurrentHashMapV8.Node<K,V>[] nextTable
      The next table to use; non-null only while resizing.

    • baseCount

      private transient volatile long baseCount
      Base counter value, used mainly when there is no contention, but also as a fallback during table initialization races. Updated via CAS.

    • sizeCtl

      private transient volatile int sizeCtl
      Table initialization and resizing control. When negative, the table is being initialized or resized: -1 for initialization, else -(1 + the number of active resizing threads). Otherwise, when table is null, holds the initial table size to use upon creation, or 0 for default. After initialization, holds the next element count value upon which to resize the table.

    • transferIndex

      private transient volatile int transferIndex
      The next table index (plus one) to split while resizing.

    • transferOrigin

      private transient volatile int transferOrigin
      The least available table index to split while resizing.

    • cellsBusy

      private transient volatile int cellsBusy
      Spinlock (locked via CAS) used when resizing and/or creating CounterCells.

    • counterCells

      private transient volatile ConcurrentHashMapV8.CounterCell[] counterCells
      Table of counter cells. When non-null, size is a power of 2.

    • keySet

      private transient ConcurrentHashMapV8.KeySetView<K,V> keySet

    • values

      private transient ConcurrentHashMapV8.ValuesView<K,V> values

    • entrySet

      private transient ConcurrentHashMapV8.EntrySetView<K,V> entrySet

    • counterHashCodeGenerator

      static final AtomicInteger counterHashCodeGenerator
      Generates initial value for per-thread CounterHashCodes.

    • SEED_INCREMENT

      static final int SEED_INCREMENT
      Increment for counterHashCodeGenerator. See class ThreadLocal for explanation.
      See Also:

    • threadCounterHashCode

      static final ThreadLocal<ConcurrentHashMapV8.CounterHashCode> threadCounterHashCode
      Per-thread counter hash codes. Shared across all instances.

    • U

      private static final sun.misc.Unsafe U

    • SIZECTL

      private static final long SIZECTL

    • TRANSFERINDEX

      private static final long TRANSFERINDEX

    • TRANSFERORIGIN

      private static final long TRANSFERORIGIN

    • BASECOUNT

      private static final long BASECOUNT

    • CELLSBUSY

      private static final long CELLSBUSY

    • CELLVALUE

      private static final long CELLVALUE

    • ABASE

      private static final long ABASE

    • ASHIFT

      private static final int ASHIFT

  • Constructor Details

    • ConcurrentHashMapV8

      ConcurrentHashMapV8()
      Creates a new, empty map with the default initial table size (16).

    • ConcurrentHashMapV8

      ConcurrentHashMapV8(int initialCapacity)
      Creates a new, empty map with an initial table size accommodating the specified number of elements without the need to dynamically resize.
      Parameters:
      initialCapacity - The implementation performs internal sizing to accommodate this many elements.
      Throws:
      IllegalArgumentException - if the initial capacity of elements is negative

    • ConcurrentHashMapV8

      ConcurrentHashMapV8(Map<? extends K,? extends V> m)
      Creates a new map with the same mappings as the given map.
      Parameters:
      m - the map

    • ConcurrentHashMapV8

      ConcurrentHashMapV8(int initialCapacity, float loadFactor)
      Creates a new, empty map with an initial table size based on the given number of elements (initialCapacity) and initial table density (loadFactor).
      Parameters:
      initialCapacity - the initial capacity. The implementation performs internal sizing to accommodate this many elements, given the specified load factor.
      loadFactor - the load factor (table density) for establishing the initial table size
      Throws:
      IllegalArgumentException - if the initial capacity of elements is negative or the load factor is nonpositive
      Since:
      1.6

    • ConcurrentHashMapV8

      ConcurrentHashMapV8(int initialCapacity, float loadFactor, int concurrencyLevel)
      Creates a new, empty map with an initial table size based on the given number of elements (initialCapacity), table density (loadFactor), and number of concurrently updating threads (concurrencyLevel).
      Parameters:
      initialCapacity - the initial capacity. The implementation performs internal sizing to accommodate this many elements, given the specified load factor.
      loadFactor - the load factor (table density) for establishing the initial table size
      concurrencyLevel - the estimated number of concurrently updating threads. The implementation may use this value as a sizing hint.
      Throws:
      IllegalArgumentException - if the initial capacity is negative or the load factor or concurrencyLevel are nonpositive

  • Method Details

    • spread

      static final int spread(int h)
      Spreads (XORs) higher bits of hash to lower and also forces top bit to 0. Because the table uses power-of-two masking, sets of hashes that vary only in bits above the current mask will always collide. (Among known examples are sets of Float keys holding consecutive whole numbers in small tables.) So we apply a transform that spreads the impact of higher bits downward. There is a tradeoff between speed, utility, and quality of bit-spreading. Because many common sets of hashes are already reasonably distributed (so don't benefit from spreading), and because we use trees to handle large sets of collisions in bins, we just XOR some shifted bits in the cheapest possible way to reduce systematic lossage, as well as to incorporate impact of the highest bits that would otherwise never be used in index calculations because of table bounds.

    • tableSizeFor

      private static final int tableSizeFor(int c)
      Returns a power of two table size for the given desired capacity. See Hackers Delight, sec 3.2

    • comparableClassFor

      static Class<?> comparableClassFor(Object x)
      Returns x's Class if it is of the form "class C implements Comparable", else null.

    • compareComparables

      static int compareComparables(Class<?> kc, Object k, Object x)
      Returns k.compareTo(x) if x matches kc (k's screened comparable class), else 0.

    • tabAt

      static final <K, V> ConcurrentHashMapV8.Node<K,V> tabAt(ConcurrentHashMapV8.Node<K,V>[] tab, int i)

    • casTabAt

      static final <K, V> boolean casTabAt(ConcurrentHashMapV8.Node<K,V>[] tab, int i, ConcurrentHashMapV8.Node<K,V> c, ConcurrentHashMapV8.Node<K,V> v)

    • setTabAt

      static final <K, V> void setTabAt(ConcurrentHashMapV8.Node<K,V>[] tab, int i, ConcurrentHashMapV8.Node<K,V> v)

    • size

      public int size()
      Specified by:
      size in interface Map<K,V>
      Overrides:
      size in class AbstractMap<K,V>

    • isEmpty

      public boolean isEmpty()
      Specified by:
      isEmpty in interface Map<K,V>
      Overrides:
      isEmpty in class AbstractMap<K,V>

    • get

      public V 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.)

      Specified by:
      get in interface Map<K,V>
      Overrides:
      get in class AbstractMap<K,V>
      Throws:
      NullPointerException - if the specified key is null

    • containsKey

      public boolean containsKey(Object key)
      Tests if the specified object is a key in this table.
      Specified by:
      containsKey in interface Map<K,V>
      Overrides:
      containsKey in class AbstractMap<K,V>
      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:
      NullPointerException - if the specified key is null

    • containsValue

      public boolean containsValue(Object value)
      Returns true if this map maps one or more keys to the specified value. Note: This method may require a full traversal of the map, and is much slower than method containsKey.
      Specified by:
      containsValue in interface Map<K,V>
      Overrides:
      containsValue in class AbstractMap<K,V>
      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:
      NullPointerException - if the specified value is null

    • put

      public V put(K 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 interface Map<K,V>
      Overrides:
      put in class AbstractMap<K,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:
      NullPointerException - if the specified key or value is null

    • putVal

      final V putVal(K key, V value, boolean onlyIfAbsent)
      Implementation for put and putIfAbsent

    • putAll

      public void putAll(Map<? extends K,? extends V> m)
      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.
      Specified by:
      putAll in interface Map<K,V>
      Overrides:
      putAll in class AbstractMap<K,V>
      Parameters:
      m - mappings to be stored in this map

    • remove

      public V 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.
      Specified by:
      remove in interface Map<K,V>
      Overrides:
      remove in class AbstractMap<K,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:
      NullPointerException - if the specified key is null

    • replaceNode

      final V replaceNode(Object key, V value, Object cv)
      Implementation for the four public remove/replace methods: Replaces node value with v, conditional upon match of cv if non-null. If resulting value is null, delete.

    • clear

      public void clear()
      Removes all of the mappings from this map.
      Specified by:
      clear in interface Map<K,V>
      Overrides:
      clear in class AbstractMap<K,V>

    • keySet

      public ConcurrentHashMapV8.KeySetView<K,V> 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.

      Specified by:
      keySet in interface Map<K,V>
      Overrides:
      keySet in class AbstractMap<K,V>
      Returns:
      the set view

    • values

      public Collection<V> 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.

      Specified by:
      values in interface Map<K,V>
      Overrides:
      values in class AbstractMap<K,V>
      Returns:
      the collection view

    • entrySet

      public Set<Map.Entry<K,V>> 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.

      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.

      Specified by:
      entrySet in interface Map<K,V>
      Specified by:
      entrySet in class AbstractMap<K,V>
      Returns:
      the set view

    • hashCode

      public int hashCode()
      Returns the hash code value for this Map, i.e., the sum of, for each key-value pair in the map, key.hashCode() ^ value.hashCode().
      Specified by:
      hashCode in interface Map<K,V>
      Overrides:
      hashCode in class AbstractMap<K,V>
      Returns:
      the hash code value for this map

    • toString

      public String toString()
      Returns a string representation of this map. The string representation consists of a list of key-value mappings (in no particular order) 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.
      Overrides:
      toString in class AbstractMap<K,V>
      Returns:
      a string representation of this map

    • equals

      public boolean equals(Object o)
      Compares the specified object with this map for equality. Returns true if the given object is a map with the same mappings as this map. This operation may return misleading results if either map is concurrently modified during execution of this method.
      Specified by:
      equals in interface Map<K,V>
      Overrides:
      equals in class AbstractMap<K,V>
      Parameters:
      o - object to be compared for equality with this map
      Returns:
      true if the specified object is equal to this map

    • writeObject

      private void writeObject(ObjectOutputStream s) throws IOException
      Saves the state of the ConcurrentHashMapV8 instance to a stream (i.e., serializes it).
      Parameters:
      s - the stream
      Throws:
      IOException - if an I/O error occurs

    • readObject

      private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException
      Reconstitutes the instance from a stream (that is, deserializes it).
      Parameters:
      s - the stream
      Throws:
      ClassNotFoundException - if the class of a serialized object could not be found
      IOException - if an I/O error occurs

    • putIfAbsent

      public V putIfAbsent(K key, V value)
      Specified by:
      putIfAbsent in interface ConcurrentMap<K,V>
      Specified by:
      putIfAbsent in interface Map<K,V>
      Returns:
      the previous value associated with the specified key, or null if there was no mapping for the key
      Throws:
      NullPointerException - if the specified key or value is null

    • remove

      public boolean remove(Object key, Object value)
      Specified by:
      remove in interface ConcurrentMap<K,V>
      Specified by:
      remove in interface Map<K,V>
      Throws:
      NullPointerException - if the specified key is null

    • replace

      public boolean replace(K key, V oldValue, V newValue)
      Specified by:
      replace in interface ConcurrentMap<K,V>
      Specified by:
      replace in interface Map<K,V>
      Throws:
      NullPointerException - if any of the arguments are null

    • replace

      public V replace(K key, V value)
      Specified by:
      replace in interface ConcurrentMap<K,V>
      Specified by:
      replace in interface Map<K,V>
      Returns:
      the previous value associated with the specified key, or null if there was no mapping for the key
      Throws:
      NullPointerException - if the specified key or value is null

    • getOrDefault

      public V getOrDefault(Object key, V defaultValue)
      Returns the value to which the specified key is mapped, or the given default value if this map contains no mapping for the key.
      Specified by:
      getOrDefault in interface ConcurrentMap<K,V>
      Specified by:
      getOrDefault in interface Map<K,V>
      Parameters:
      key - the key whose associated value is to be returned
      defaultValue - the value to return if this map contains no mapping for the given key
      Returns:
      the mapping for the key, if present; else the default value
      Throws:
      NullPointerException - if the specified key is null

    • contains

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

    • keys

      public Enumeration<K> keys()
      Returns an enumeration of the keys in this table.
      Returns:
      an enumeration of the keys in this table
      See Also:

    • elements

      public Enumeration<V> elements()
      Returns an enumeration of the values in this table.
      Returns:
      an enumeration of the values in this table
      See Also:

    • mappingCount

      public long mappingCount()
      Returns the number of mappings. This method should be used instead of size() because a ConcurrentHashMapV8 may contain more mappings than can be represented as an int. The value returned is an estimate; the actual count may differ if there are concurrent insertions or removals.
      Returns:
      the number of mappings
      Since:
      1.8

    • newKeySet

      public static <K> ConcurrentHashMapV8.KeySetView<K,Boolean> newKeySet()
      Creates a new Set backed by a ConcurrentHashMapV8 from the given type to Boolean.TRUE.
      Returns:
      the new set
      Since:
      1.8

    • newKeySet

      public static <K> ConcurrentHashMapV8.KeySetView<K,Boolean> newKeySet(int initialCapacity)
      Creates a new Set backed by a ConcurrentHashMapV8 from the given type to Boolean.TRUE.
      Parameters:
      initialCapacity - The implementation performs internal sizing to accommodate this many elements.
      Returns:
      the new set
      Throws:
      IllegalArgumentException - if the initial capacity of elements is negative
      Since:
      1.8

    • keySet

      public ConcurrentHashMapV8.KeySetView<K,V> keySet(V mappedValue)
      Returns a Set view of the keys in this map, using the given common mapped value for any additions (i.e., Collection.add(E) and Collection.addAll(Collection)). This is of course only appropriate if it is acceptable to use the same value for all additions from this view.
      Parameters:
      mappedValue - the mapped value to use for any additions
      Returns:
      the set view
      Throws:
      NullPointerException - if the mappedValue is null

    • initTable

      private final ConcurrentHashMapV8.Node<K,V>[] initTable()
      Initializes table, using the size recorded in sizeCtl.

    • addCount

      private final void addCount(long x, int check)
      Adds to count, and if table is too small and not already resizing, initiates transfer. If already resizing, helps perform transfer if work is available. Rechecks occupancy after a transfer to see if another resize is already needed because resizings are lagging additions.
      Parameters:
      x - the count to add
      check - if invalid input: '<'0, don't check resize, if invalid input: '<'= 1 only check if uncontended

    • helpTransfer

      final ConcurrentHashMapV8.Node<K,V>[] helpTransfer(ConcurrentHashMapV8.Node<K,V>[] tab, ConcurrentHashMapV8.Node<K,V> f)
      Helps transfer if a resize is in progress.

    • tryPresize

      private final void tryPresize(int size)
      Tries to presize table to accommodate the given number of elements.
      Parameters:
      size - number of elements (doesn't need to be perfectly accurate)

    • transfer

      private final void transfer(ConcurrentHashMapV8.Node<K,V>[] tab, ConcurrentHashMapV8.Node<K,V>[] nextTab)
      Moves and/or copies the nodes in each bin to new table. See above for explanation.

    • treeifyBin

      private final void treeifyBin(ConcurrentHashMapV8.Node<K,V>[] tab, int index)
      Replaces all linked nodes in bin at given index unless table is too small, in which case resizes instead.

    • untreeify

      static <K, V> ConcurrentHashMapV8.Node<K,V> untreeify(ConcurrentHashMapV8.Node<K,V> b)
      Returns a list on non-TreeNodes replacing those in given list.

    • sumCount

      final long sumCount()

    • fullAddCount

      private final void fullAddCount(long x, ConcurrentHashMapV8.CounterHashCode hc, boolean wasUncontended)

    • getUnsafe

      private static sun.misc.Unsafe getUnsafe()
      Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. Replace with a simple call to Unsafe.getUnsafe when integrating into a jdk.
      Returns:
      a sun.misc.Unsafe