WeakHashMap. However, you can also specify hard keys and weak values, or any other combination. The default constructor uses hard keys and soft values, providing a memory-sensitive cache. This map is similar to ReferenceIdentityMap. It differs in that keys and values in this class are compared using equals().
This {@link java.util.Map Map} implementation does not allow null elements.Attempting to add a null key or value to the map will raise a NullPointerException.
This implementation is not synchronized. You can use {@link java.util.Collections#synchronizedMap} toprovide synchronized access to a ReferenceMap. Remember that synchronization will not stop the garbage collecter removing entries.
All the available iterators can be reset back to the start by casting to ResettableIterator and calling reset().
Note that ReferenceMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. The simplest approach is to wrap this map using {@link java.util.Collections#synchronizedMap}. This class may throw exceptions when accessed by concurrent threads without synchronization.
NOTE: As from Commons Collections 3.1 this map extends AbstractReferenceMap (previously it extended AbstractMap). As a result, the implementation is now extensible and provides a MapIterator.
@see java.lang.ref.Reference
@since Commons Collections 3.0 (previously in main package v2.1)
@version $Revision$ $Date$
@author Paul Jack
@author Stephen Colebourne
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