Package org.apache.groovy.util.concurrent.concurrentlinkedhashmap

Class ConcurrentLinkedHashMap<K,​V>

java.lang.Object
java.util.AbstractMap<K,​V>
org.apache.groovy.util.concurrent.concurrentlinkedhashmap.ConcurrentLinkedHashMap<K,​V>
Type Parameters:
K - the type of keys maintained by this map
V - the type of mapped values
All Implemented Interfaces:
java.io.Serializable, java.util.concurrent.ConcurrentMap<K,​V>, java.util.Map<K,​V>
@ThreadSafe
public final class ConcurrentLinkedHashMap<K,​V>
extends java.util.AbstractMap<K,​V>
implements java.util.concurrent.ConcurrentMap<K,​V>, java.io.Serializable
A hash table supporting full concurrency of retrievals, adjustable expected concurrency for updates, and a maximum capacity to bound the map by. This implementation differs from ConcurrentHashMap in that it maintains a page replacement algorithm that is used to evict an entry when the map has exceeded its capacity. Unlike the Java Collections Framework, this map does not have a publicly visible constructor and instances are created through a ConcurrentLinkedHashMap.Builder.

An entry is evicted from the map when the weighted capacity exceeds its maximum weighted capacity threshold. A EntryWeigher determines how many units of capacity that an entry consumes. The default weigher assigns each value a weight of 1 to bound the map by the total number of key-value pairs. A map that holds collections may choose to weigh values by the number of elements in the collection and bound the map by the total number of elements that it contains. A change to a value that modifies its weight requires that an update operation is performed on the map.

An EvictionListener may be supplied for notification when an entry is evicted from the map. This listener is invoked on a caller's thread and will not block other threads from operating on the map. An implementation should be aware that the caller's thread will not expect long execution times or failures as a side effect of the listener being notified. Execution safety and a fast turn around time can be achieved by performing the operation asynchronously, such as by submitting a task to an ExecutorService.

The concurrency level determines the number of threads that can concurrently modify the table. Using a significantly higher or lower value than needed can waste space or lead to thread contention, but an estimate within an order of magnitude of the ideal value does not usually have a noticeable impact. Because placement in hash tables is essentially random, the actual concurrency will vary.

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. Unlike LinkedHashMap, this class does not provide predictable iteration order. A snapshot of the keys and entries may be obtained in ascending and descending order of retention.

See Also:
http://code.google.com/p/concurrentlinkedhashmap/, Serialized Form

  • Nested Class Summary

    Nested Classes
    Modifier and Type Class Description
    static class  ConcurrentLinkedHashMap.Builder<K,​V>
    A builder that creates ConcurrentLinkedHashMap instances.

    Nested classes/interfaces inherited from class java.util.AbstractMap

    java.util.AbstractMap.SimpleEntry<K extends java.lang.Object,​V extends java.lang.Object>, java.util.AbstractMap.SimpleImmutableEntry<K extends java.lang.Object,​V extends java.lang.Object>

    Nested classes/interfaces inherited from interface java.util.Map

    java.util.Map.Entry<K extends java.lang.Object,​V extends java.lang.Object>

  • Method Summary

    Modifier and Type Method Description
    java.util.Set<K> ascendingKeySet()
    Returns a unmodifiable snapshot Set view of the keys contained in this map.
    java.util.Set<K> ascendingKeySetWithLimit​(int limit)
    Returns an unmodifiable snapshot Set view of the keys contained in this map.
    java.util.Map<K,​V> ascendingMap()
    Returns an unmodifiable snapshot Map view of the mappings contained in this map.
    java.util.Map<K,​V> ascendingMapWithLimit​(int limit)
    Returns an unmodifiable snapshot Map view of the mappings contained in this map.
    long capacity()
    Retrieves the maximum weighted capacity of the map.
    void clear()  
    V computeIfAbsent​(K key, java.util.function.Function<? super K,​? extends V> mappingFunction)
    If the specified key is not already associated with a value, attempts to compute its value using the given mapping function and enters it into this map unless null.
    boolean containsKey​(java.lang.Object key)  
    boolean containsValue​(java.lang.Object value)  
    java.util.Set<K> descendingKeySet()
    Returns an unmodifiable snapshot Set view of the keys contained in this map.
    java.util.Set<K> descendingKeySetWithLimit​(int limit)
    Returns an unmodifiable snapshot Set view of the keys contained in this map.
    java.util.Map<K,​V> descendingMap()
    Returns an unmodifiable snapshot Map view of the mappings contained in this map.
    java.util.Map<K,​V> descendingMapWithLimit​(int limit)
    Returns an unmodifiable snapshot Map view of the mappings contained in this map.
    java.util.Set<java.util.Map.Entry<K,​V>> entrySet()  
    V get​(java.lang.Object key)  
    V getQuietly​(java.lang.Object key)
    Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
    boolean isEmpty()  
    java.util.Set<K> keySet()  
    V put​(K key, V value)  
    V putIfAbsent​(K key, V value)  
    V remove​(java.lang.Object key)  
    boolean remove​(java.lang.Object key, java.lang.Object value)  
    V replace​(K key, V value)  
    boolean replace​(K key, V oldValue, V newValue)  
    void setCapacity​(long capacity)
    Sets the maximum weighted capacity of the map and eagerly evicts entries until it shrinks to the appropriate size.
    int size()  
    java.util.Collection<V> values()  
    long weightedSize()
    Returns the weighted size of this map.

    Methods inherited from class java.util.AbstractMap

    clone, equals, hashCode, putAll, toString

    Methods inherited from class java.lang.Object

    finalize, getClass, notify, notifyAll, wait, wait, wait

    Methods inherited from interface java.util.concurrent.ConcurrentMap

    compute, computeIfPresent, forEach, getOrDefault, merge, replaceAll

    Methods inherited from interface java.util.Map

    equals, hashCode, putAll

  • Method Details

    • capacity

      public long capacity()
      Retrieves the maximum weighted capacity of the map.
      Returns:
      the maximum weighted capacity

    • setCapacity

      public void setCapacity​(long capacity)
      Sets the maximum weighted capacity of the map and eagerly evicts entries until it shrinks to the appropriate size.
      Parameters:
      capacity - the maximum weighted capacity of the map
      Throws:
      java.lang.IllegalArgumentException - if the capacity is negative

    • isEmpty

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

    • size

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

    • weightedSize

      public long weightedSize()
      Returns the weighted size of this map.
      Returns:
      the combined weight of the values in this map

    • clear

      public void clear()
      Specified by:
      clear in interface java.util.Map<K,​V>
      Overrides:
      clear in class java.util.AbstractMap<K,​V>

    • containsKey

      public boolean containsKey​(java.lang.Object key)
      Specified by:
      containsKey in interface java.util.Map<K,​V>
      Overrides:
      containsKey in class java.util.AbstractMap<K,​V>

    • containsValue

      public boolean containsValue​(java.lang.Object value)
      Specified by:
      containsValue in interface java.util.Map<K,​V>
      Overrides:
      containsValue in class java.util.AbstractMap<K,​V>

    • get

      public V get​(java.lang.Object key)
      Specified by:
      get in interface java.util.Map<K,​V>
      Overrides:
      get in class java.util.AbstractMap<K,​V>

    • getQuietly

      public V getQuietly​(java.lang.Object key)
      Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key. This method differs from get(Object) in that it does not record the operation with the page replacement policy.
      Parameters:
      key - the key whose associated value is to be returned
      Returns:
      the value to which the specified key is mapped, or null if this map contains no mapping for the key
      Throws:
      java.lang.NullPointerException - if the specified key is null

    • put

      public V put​(K key, V value)
      Specified by:
      put in interface java.util.Map<K,​V>
      Overrides:
      put in class java.util.AbstractMap<K,​V>

    • putIfAbsent

      public V putIfAbsent​(K key, V value)
      Specified by:
      putIfAbsent in interface java.util.concurrent.ConcurrentMap<K,​V>
      Specified by:
      putIfAbsent in interface java.util.Map<K,​V>

    • computeIfAbsent

      public V computeIfAbsent​(K key, java.util.function.Function<? super K,​? extends V> mappingFunction)
      If the specified key is not already associated with a value, attempts to compute its value using the given mapping function and enters it into this map unless null. The entire method invocation is performed atomically, so the function is applied at most once per key. Some attempted update operations on this map by other threads may be blocked while computation is in progress, so the computation should be short and simple, and must not attempt to update any other mappings of this map.
      Specified by:
      computeIfAbsent in interface java.util.concurrent.ConcurrentMap<K,​V>
      Specified by:
      computeIfAbsent in interface java.util.Map<K,​V>
      Parameters:
      key - key with which the specified value is to be associated
      mappingFunction - the function to compute a value
      Returns:
      the current (existing or computed) value associated with the specified key, or null if the computed value is null
      Throws:
      java.lang.NullPointerException - if the specified key or mappingFunction is null
      java.lang.IllegalStateException - if the computation detectably attempts a recursive update to this map that would otherwise never complete
      java.lang.RuntimeException - or Error if the mappingFunction does so, in which case the mapping is left unestablished

    • remove

      public V remove​(java.lang.Object key)
      Specified by:
      remove in interface java.util.Map<K,​V>
      Overrides:
      remove in class java.util.AbstractMap<K,​V>

    • remove

      public boolean remove​(java.lang.Object key, java.lang.Object value)
      Specified by:
      remove in interface java.util.concurrent.ConcurrentMap<K,​V>
      Specified by:
      remove in interface java.util.Map<K,​V>

    • replace

      public V replace​(K key, V value)
      Specified by:
      replace in interface java.util.concurrent.ConcurrentMap<K,​V>
      Specified by:
      replace in interface java.util.Map<K,​V>

    • replace

      public boolean replace​(K key, V oldValue, V newValue)
      Specified by:
      replace in interface java.util.concurrent.ConcurrentMap<K,​V>
      Specified by:
      replace in interface java.util.Map<K,​V>

    • keySet

      public java.util.Set<K> keySet()
      Specified by:
      keySet in interface java.util.Map<K,​V>
      Overrides:
      keySet in class java.util.AbstractMap<K,​V>

    • ascendingKeySet

      public java.util.Set<K> ascendingKeySet()
      Returns a unmodifiable snapshot Set view of the keys contained in this map. The set's iterator returns the keys whose order of iteration is the ascending order in which its entries are considered eligible for retention, from the least-likely to be retained to the most-likely.

      Beware that, unlike in keySet(), obtaining the set is NOT a constant-time operation. Because of the asynchronous nature of the page replacement policy, determining the retention ordering requires a traversal of the keys.

      Returns:
      an ascending snapshot view of the keys in this map

    • ascendingKeySetWithLimit

      public java.util.Set<K> ascendingKeySetWithLimit​(int limit)
      Returns an unmodifiable snapshot Set view of the keys contained in this map. The set's iterator returns the keys whose order of iteration is the ascending order in which its entries are considered eligible for retention, from the least-likely to be retained to the most-likely.

      Beware that, unlike in keySet(), obtaining the set is NOT a constant-time operation. Because of the asynchronous nature of the page replacement policy, determining the retention ordering requires a traversal of the keys.

      Parameters:
      limit - the maximum size of the returned set
      Returns:
      a ascending snapshot view of the keys in this map
      Throws:
      java.lang.IllegalArgumentException - if the limit is negative

    • descendingKeySet

      public java.util.Set<K> descendingKeySet()
      Returns an unmodifiable snapshot Set view of the keys contained in this map. The set's iterator returns the keys whose order of iteration is the descending order in which its entries are considered eligible for retention, from the most-likely to be retained to the least-likely.

      Beware that, unlike in keySet(), obtaining the set is NOT a constant-time operation. Because of the asynchronous nature of the page replacement policy, determining the retention ordering requires a traversal of the keys.

      Returns:
      a descending snapshot view of the keys in this map

    • descendingKeySetWithLimit

      public java.util.Set<K> descendingKeySetWithLimit​(int limit)
      Returns an unmodifiable snapshot Set view of the keys contained in this map. The set's iterator returns the keys whose order of iteration is the descending order in which its entries are considered eligible for retention, from the most-likely to be retained to the least-likely.

      Beware that, unlike in keySet(), obtaining the set is NOT a constant-time operation. Because of the asynchronous nature of the page replacement policy, determining the retention ordering requires a traversal of the keys.

      Parameters:
      limit - the maximum size of the returned set
      Returns:
      a descending snapshot view of the keys in this map
      Throws:
      java.lang.IllegalArgumentException - if the limit is negative

    • values

      public java.util.Collection<V> values()
      Specified by:
      values in interface java.util.Map<K,​V>
      Overrides:
      values in class java.util.AbstractMap<K,​V>

    • entrySet

      public java.util.Set<java.util.Map.Entry<K,​V>> entrySet()
      Specified by:
      entrySet in interface java.util.Map<K,​V>
      Specified by:
      entrySet in class java.util.AbstractMap<K,​V>

    • ascendingMap

      public java.util.Map<K,​V> ascendingMap()
      Returns an unmodifiable snapshot Map view of the mappings contained in this map. The map's collections return the mappings whose order of iteration is the ascending order in which its entries are considered eligible for retention, from the least-likely to be retained to the most-likely.

      Beware that obtaining the mappings is NOT a constant-time operation. Because of the asynchronous nature of the page replacement policy, determining the retention ordering requires a traversal of the entries.

      Returns:
      a ascending snapshot view of this map

    • ascendingMapWithLimit

      public java.util.Map<K,​V> ascendingMapWithLimit​(int limit)
      Returns an unmodifiable snapshot Map view of the mappings contained in this map. The map's collections return the mappings whose order of iteration is the ascending order in which its entries are considered eligible for retention, from the least-likely to be retained to the most-likely.

      Beware that obtaining the mappings is NOT a constant-time operation. Because of the asynchronous nature of the page replacement policy, determining the retention ordering requires a traversal of the entries.

      Parameters:
      limit - the maximum size of the returned map
      Returns:
      a ascending snapshot view of this map
      Throws:
      java.lang.IllegalArgumentException - if the limit is negative

    • descendingMap

      public java.util.Map<K,​V> descendingMap()
      Returns an unmodifiable snapshot Map view of the mappings contained in this map. The map's collections return the mappings whose order of iteration is the descending order in which its entries are considered eligible for retention, from the most-likely to be retained to the least-likely.

      Beware that obtaining the mappings is NOT a constant-time operation. Because of the asynchronous nature of the page replacement policy, determining the retention ordering requires a traversal of the entries.

      Returns:
      a descending snapshot view of this map

    • descendingMapWithLimit

      public java.util.Map<K,​V> descendingMapWithLimit​(int limit)
      Returns an unmodifiable snapshot Map view of the mappings contained in this map. The map's collections return the mappings whose order of iteration is the descending order in which its entries are considered eligible for retention, from the most-likely to be retained to the least-likely.

      Beware that obtaining the mappings is NOT a constant-time operation. Because of the asynchronous nature of the page replacement policy, determining the retention ordering requires a traversal of the entries.

      Parameters:
      limit - the maximum size of the returned map
      Returns:
      a descending snapshot view of this map
      Throws:
      java.lang.IllegalArgumentException - if the limit is negative