Package org.geotools.util

Class SoftValueHashMap<K,V>

Object
AbstractMap<K,V>
SoftValueHashMap<K,V>
Type Parameters:
K - The type of keys in the map.
V - The type of values in the map.
All Implemented Interfaces:
Map<K,V>
public class SoftValueHashMap<K,V> extends AbstractMap<K,V>
A hash map implementation that uses soft references, leaving memory when an entry is not used anymore and memory is low.

This map implementation actually maintains some of the first entries as hard references. Only oldest entries are retained by soft references, in order to avoid too aggressive garbage collection. The amount of entries to retain by hard reference is specified at construction time.

This map is thread-safe. It accepts the null key; it does not accept the null value. Usage of value, key or entry collections are supported. The iterator on the ConcurrentHashMap is weakly consistent.

Since:
2.3
Author:
Simone Giannecchini, Martin Desruisseaux, Ugo Moschini

  • Field Details

  • Constructor Details

    • SoftValueHashMap

      public SoftValueHashMap()
      Creates a map with the default hard references count.

    • SoftValueHashMap

      public SoftValueHashMap(int hardReferencesCount)
      Creates a map with the specified hard references count.
      Parameters:
      hardReferencesCount - The maximal number of hard references to keep.

    • SoftValueHashMap

      public SoftValueHashMap(int hardReferencesCount, SoftValueHashMap.ValueCleaner cleaner)
      Creates a map with the specified hard references count.
      Parameters:
      hardReferencesCount - The maximal number of hard references to keep.

  • Method Details

    • getHardReferencesCount

      public int getHardReferencesCount()
      Returns the number of hard references kept in this cache

    • size

      public int size()
      Returns the number of entries in this map.
      Specified by:
      size in interface Map<K,V>
      Overrides:
      size in class AbstractMap<K,V>

    • containsKey

      public boolean containsKey(Object key)
      Returns true if this map contains a mapping for the specified key.
      Specified by:
      containsKey in interface Map<K,V>
      Overrides:
      containsKey in class AbstractMap<K,V>

    • containsValue

      public boolean containsValue(Object value)
      Returns true if this map maps one or more keys to this value.
      Specified by:
      containsValue in interface Map<K,V>
      Overrides:
      containsValue in class AbstractMap<K,V>

    • get

      public V get(Object key)
      Returns the value to which this map maps the specified key. Returns null if the map contains no mapping for this key, or the value has been garbage collected.
      Specified by:
      get in interface Map<K,V>
      Overrides:
      get in class AbstractMap<K,V>
      Parameters:
      key - key whose associated value is to be returned.
      Returns:
      the value to which this map maps the specified key, or null if none.

    • put

      public V put(K key, V value)
      Associates the specified value with the specified key in this map.
      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. The value can't be null.
      Returns:
      Previous value associated with specified key, or null if there was no mapping for key.

    • putAll

      public void putAll(Map<? extends K,? extends V> map)
      Copies all of the mappings from the specified map to this map.
      Specified by:
      putAll in interface Map<K,V>
      Overrides:
      putAll in class AbstractMap<K,V>
      Parameters:
      map - Mappings to be stored in this map.

    • remove

      public V remove(Object key)
      Removes the mapping for this key from this map if present.
      Specified by:
      remove in interface Map<K,V>
      Overrides:
      remove in class AbstractMap<K,V>
      Parameters:
      key - Key whose mapping is to be removed from the map.
      Returns:
      previous value associated with specified key, or null if there was no entry for key.

    • clear

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

    • entrySet

      public Set<Map.Entry<K,V>> entrySet()
      Returns a set view of the mappings contained in this map.
      Specified by:
      entrySet in interface Map<K,V>
      Specified by:
      entrySet in class AbstractMap<K,V>

    • equals

      public boolean equals(Object object)
      Compares the specified object with this map for equality.
      Specified by:
      equals in interface Map<K,V>
      Overrides:
      equals in class AbstractMap<K,V>
      Parameters:
      object - The object to compare with this map for equality.

    • hashCode

      public int hashCode()
      Returns the hash code value for this map.
      Specified by:
      hashCode in interface Map<K,V>
      Overrides:
      hashCode in class AbstractMap<K,V>

    • toString

      public String toString()
      Returns a string representation of this map.
      Overrides:
      toString in class AbstractMap<K,V>