Package rs.baselib.util

Class WeakMapCache<K,​V>

java.lang.Object
rs.baselib.util.WeakMapCache<K,​V>
All Implemented Interfaces:
ICache<K,​V>
public class WeakMapCache<K,​V>
extends java.lang.Object
implements ICache<K,​V>
A cache implementation using a HashMap with WeakReferences.
Author:
ralph

  • Constructor Summary

    Constructors 
    Constructor Description
    WeakMapCache()
    Constructor.

  • Method Summary

    Modifier and Type Method Description
    void clear()
    Removes all of the mappings from this map (optional operation).
    protected void clearMap()
    Clears the map by working on the reference queue.
    boolean containsKey​(java.lang.Object key)
    Returns true if this map contains a mapping for the specified key.
    boolean containsValue​(java.lang.Object value)
    Returns true if this map maps one or more keys to the specified value.
    V get​(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()
    Returns true if this map contains no key-value mappings.
    java.util.Set<K> keySet()
    Returns a Set view of the keys contained in this map.
    V put​(K key, V value)
    Associates the specified value with the specified key in this map (optional operation).
    V remove​(java.lang.Object key)
    Removes the mapping for a key from this map if it is present (optional operation).
    int size()
    Returns the number of key-value mappings in this map.
    java.util.Collection<V> values()
    Returns a Collection view of the values contained in this map.

    Methods inherited from class java.lang.Object

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

  • Constructor Details

  • Method Details

    • 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 interface ICache<K,​V>
      Returns:
      the number of key-value mappings in this map

    • isEmpty

      public boolean isEmpty()
      Returns true if this map contains no key-value mappings.
      Specified by:
      isEmpty in interface ICache<K,​V>
      Returns:
      true if this map contains no key-value mappings

    • containsKey

      public boolean containsKey​(java.lang.Object key)
      Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains a mapping for a key k such that (key==null ? k==null : key.equals(k)). (There can be at most one such mapping.)
      Specified by:
      containsKey in interface ICache<K,​V>
      Parameters:
      key - key whose presence in this map is to be tested
      Returns:
      true if this map contains a mapping for the specified key

    • containsValue

      public boolean containsValue​(java.lang.Object value)
      Returns true if this map maps one or more keys to the specified value. More formally, returns true if and only if this map contains at least one mapping to a value v such that (value==null ? v==null : value.equals(v)). This operation will probably require time linear in the map size for most implementations of the Map interface.
      Specified by:
      containsValue in interface ICache<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

    • get

      public V get​(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.

      More formally, if this map contains a mapping from a key k to a value v such that (key==null ? k==null : key.equals(k)), then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

      If this map permits null values, then a return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

      Specified by:
      get in interface ICache<K,​V>
      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

    • clearMap

      protected void clearMap()
      Clears the map by working on the reference queue.

    • put

      public V put​(K key, V value)
      Associates the specified value with the specified key in this map (optional operation). If the map previously contained a mapping for the key, the old value is replaced by the specified value. (A map m is said to contain a mapping for a key k if and only if m.containsKey(k) would return true.)
      Specified by:
      put in interface ICache<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. (A null return can also indicate that the map previously associated null with key, if the implementation supports null values.)

    • remove

      public V remove​(java.lang.Object key)
      Removes the mapping for a key from this map if it is present (optional operation). More formally, if this map contains a mapping from key k to value v such that (key==null ? k==null : key.equals(k)), that mapping is removed. (The map can contain at most one such mapping.)

      Returns the value to which this map previously associated the key, or null if the map contained no mapping for the key.

      If this map permits null values, then a return value of null does not necessarily indicate that the map contained no mapping for the key; it's also possible that the map explicitly mapped the key to null.

      The map will not contain a mapping for the specified key once the call returns.

      Specified by:
      remove in interface ICache<K,​V>
      Parameters:
      key - key whose mapping is to be removed from the map
      Returns:
      the previous value associated with key, or null if there was no mapping for key.

    • clear

      public void clear()
      Removes all of the mappings from this map (optional operation). The map will be empty after this call returns.
      Specified by:
      clear in interface ICache<K,​V>

    • keySet

      public java.util.Set<K> 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. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.
      Specified by:
      keySet in interface ICache<K,​V>
      Returns:
      a set view of the keys contained in this map

    • values

      public java.util.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. If the map is modified while an iteration over the collection is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.
      Specified by:
      values in interface ICache<K,​V>
      Returns:
      a collection view of the values contained in this map