Class WeakValueHashMap

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Cloneable, java.util.Map

    public class WeakValueHashMap
    extends java.util.HashMap
    A WeakValueHashMap is implemented as a HashMap that maps keys to WeakValues. Because we don't have access to the innards of the HashMap, we have to wrap/unwrap value objects with WeakValues on every operation. Fortunately WeakValues are small, short-lived objects, so the added allocation overhead is tolerable. This implementaton directly extends java.util.HashMap.
    Author:
    Markus Fuchs
    See Also:
    HashMap, WeakReference, Serialized Form
    • Nested Class Summary

      • 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>
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      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.
      java.util.Set entrySet()
      Returns a Set view of the mappings in this map.
      java.lang.Object get​(java.lang.Object key)
      Gets the value for the given key.
      boolean isEmpty()
      Returns true if this map contains no key-value mappings.
      java.lang.Object put​(java.lang.Object key, java.lang.Object value)
      Puts a new (key,value) into the map.
      java.lang.Object remove​(java.lang.Object key)
      Removes key and value for the given key.
      int size()
      Returns the number of key-value mappings in this map.
      java.util.Collection values()
      Returns a Collection view of the values contained in this map.
      • Methods inherited from class java.util.HashMap

        clear, clone, compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, keySet, merge, putAll, putIfAbsent, remove, replace, replace, replaceAll
      • Methods inherited from class java.util.AbstractMap

        equals, hashCode, toString
      • Methods inherited from class java.lang.Object

        finalize, getClass, notify, notifyAll, wait, wait, wait
      • Methods inherited from interface java.util.Map

        equals, hashCode
    • Constructor Detail

      • WeakValueHashMap

        public WeakValueHashMap()
    • Method Detail

      • size

        public int size()
        Returns the number of key-value mappings in this map.

        Specified by:
        size in interface java.util.Map
        Overrides:
        size in class java.util.HashMap
        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 java.util.Map
        Overrides:
        isEmpty in class java.util.HashMap
        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.

        Specified by:
        containsKey in interface java.util.Map
        Overrides:
        containsKey in class java.util.HashMap
        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.

        Specified by:
        containsValue in interface java.util.Map
        Overrides:
        containsValue in class java.util.HashMap
        Parameters:
        value - value whose presence in this map is to be tested
        Returns:
        true if this map maps one or more keys to this value.
      • get

        public java.lang.Object get​(java.lang.Object key)
        Gets the value for the given key.

        Specified by:
        get in interface java.util.Map
        Overrides:
        get in class java.util.HashMap
        Parameters:
        key - key whose associated value, if any, is to be returned
        Returns:
        the value to which this map maps the specified key.
      • put

        public java.lang.Object put​(java.lang.Object key,
                                    java.lang.Object value)
        Puts a new (key,value) into the map.

        Specified by:
        put in interface java.util.Map
        Overrides:
        put in class java.util.HashMap
        Parameters:
        key - key with which the specified value is to be associated.
        value - value to be associated with the specified key.
        Returns:
        previous value associated with specified key, or null if there was no mapping for key or the value has been garbage collected by the garbage collector.
      • remove

        public java.lang.Object remove​(java.lang.Object key)
        Removes key and value for the given key.

        Specified by:
        remove in interface java.util.Map
        Overrides:
        remove in class java.util.HashMap
        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 mapping for key or the value has been garbage collected by the garbage collector.
      • entrySet

        public java.util.Set entrySet()
        Returns a Set view of the mappings in this map.

        Specified by:
        entrySet in interface java.util.Map
        Overrides:
        entrySet in class java.util.HashMap
        Returns:
        a Set view of the mappings in this map.
      • values

        public java.util.Collection values()
        Returns a Collection view of the values contained in this map.

        Specified by:
        values in interface java.util.Map
        Overrides:
        values in class java.util.HashMap
        Returns:
        a Collection view of the values contained in this map.