Package org.apache.commons.collections.map

Class AbstractReferenceMap

  • All Implemented Interfaces:
    java.util.Map, IterableMap
    Direct Known Subclasses:
    ReferenceIdentityMap, ReferenceMap
    @Deprecated(since="2021-04-30")
public abstract class AbstractReferenceMap
extends AbstractHashedMap
    Deprecated.
    Commons Collections 3 is in maintenance mode. Commons Collections 4 should be used instead.
    An abstract implementation of a hash-based map that allows the entries to be removed by the garbage collector.

    This class implements all the features necessary for a subclass reference hash-based map. Key-value entries are stored in instances of the ReferenceEntry class which can be overridden and replaced. The iterators can similarly be replaced, without the need to replace the KeySet, EntrySet and Values view classes.

    Overridable methods are provided to change the default hashing behaviour, and to change how entries are added to and removed from the map. Hopefully, all you need for unusual subclasses is here.

    When you construct an AbstractReferenceMap, you can specify what kind of references are used to store the map's keys and values. If non-hard references are used, then the garbage collector can remove mappings if a key or value becomes unreachable, or if the JVM's memory is running low. For information on how the different reference types behave, see Reference.

    Different types of references can be specified for keys and values. The keys can be configured to be weak but the values hard, in which case this class will behave like a 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 implementation does not allow null elements. Attempting to add a null key or value to the map will raise a NullPointerException.

    All the available iterators can be reset back to the start by casting to ResettableIterator and calling reset().

    This implementation is not synchronized. You can use Collections.synchronizedMap(java.util.Map<K, V>) to provide synchronized access to a ReferenceMap.

    Since:
    Commons Collections 3.1 (extracted from ReferenceMap in 3.0)
    See Also:
    Reference

    • 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>

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

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

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static int HARD
      Deprecated.
      Constant indicating that hard references should be used
      static int SOFT
      Deprecated.
      Constant indicating that soft references should be used
      static int WEAK
      Deprecated.
      Constant indicating that weak references should be used

    • Method Summary

      All Methods Instance Methods Concrete Methods Deprecated Methods 
      Modifier and Type Method Description
      void clear()
      Deprecated.
      Clears this map.
      boolean containsKey​(java.lang.Object key)
      Deprecated.
      Checks whether the map contains the specified key.
      boolean containsValue​(java.lang.Object value)
      Deprecated.
      Checks whether the map contains the specified value.
      java.util.Set entrySet()
      Deprecated.
      Returns a set view of this map's entries.
      java.lang.Object get​(java.lang.Object key)
      Deprecated.
      Gets the value mapped to the key specified.
      boolean isEmpty()
      Deprecated.
      Checks whether the map is currently empty.
      java.util.Set keySet()
      Deprecated.
      Returns a set view of this map's keys.
      MapIterator mapIterator()
      Deprecated.
      Gets a MapIterator over the reference map.
      java.lang.Object put​(java.lang.Object key, java.lang.Object value)
      Deprecated.
      Puts a key-value mapping into this map.
      java.lang.Object remove​(java.lang.Object key)
      Deprecated.
      Removes the specified mapping from this map.
      int size()
      Deprecated.
      Gets the size of the map.
      java.util.Collection values()
      Deprecated.
      Returns a collection view of this map's values.

      • Methods inherited from class java.lang.Object

        getClass, notify, notifyAll, wait, wait, wait

      • Methods inherited from interface java.util.Map

        compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

    • Field Detail

      • HARD

        public static final int HARD
        Deprecated.
        Constant indicating that hard references should be used
        See Also:
        Constant Field Values

      • SOFT

        public static final int SOFT
        Deprecated.
        Constant indicating that soft references should be used
        See Also:
        Constant Field Values

      • WEAK

        public static final int WEAK
        Deprecated.
        Constant indicating that weak references should be used
        See Also:
        Constant Field Values

    • Method Detail

      • size

        public int size()
        Deprecated.
        Gets the size of the map.
        Specified by:
        size in interface java.util.Map
        Overrides:
        size in class AbstractHashedMap
        Returns:
        the size

      • isEmpty

        public boolean isEmpty()
        Deprecated.
        Checks whether the map is currently empty.
        Specified by:
        isEmpty in interface java.util.Map
        Overrides:
        isEmpty in class AbstractHashedMap
        Returns:
        true if the map is currently size zero

      • containsKey

        public boolean containsKey​(java.lang.Object key)
        Deprecated.
        Checks whether the map contains the specified key.
        Specified by:
        containsKey in interface java.util.Map
        Overrides:
        containsKey in class AbstractHashedMap
        Parameters:
        key - the key to search for
        Returns:
        true if the map contains the key

      • containsValue

        public boolean containsValue​(java.lang.Object value)
        Deprecated.
        Checks whether the map contains the specified value.
        Specified by:
        containsValue in interface java.util.Map
        Overrides:
        containsValue in class AbstractHashedMap
        Parameters:
        value - the value to search for
        Returns:
        true if the map contains the value

      • get

        public java.lang.Object get​(java.lang.Object key)
        Deprecated.
        Gets the value mapped to the key specified.
        Specified by:
        get in interface java.util.Map
        Overrides:
        get in class AbstractHashedMap
        Parameters:
        key - the key
        Returns:
        the mapped value, null if no match

      • put

        public java.lang.Object put​(java.lang.Object key,
                            java.lang.Object value)
        Deprecated.
        Puts a key-value mapping into this map. Neither the key nor the value may be null.
        Specified by:
        put in interface java.util.Map
        Overrides:
        put in class AbstractHashedMap
        Parameters:
        key - the key to add, must not be null
        value - the value to add, must not be null
        Returns:
        the value previously mapped to this key, null if none
        Throws:
        java.lang.NullPointerException - if either the key or value is null

      • remove

        public java.lang.Object remove​(java.lang.Object key)
        Deprecated.
        Removes the specified mapping from this map.
        Specified by:
        remove in interface java.util.Map
        Overrides:
        remove in class AbstractHashedMap
        Parameters:
        key - the mapping to remove
        Returns:
        the value mapped to the removed key, null if key not in map

      • clear

        public void clear()
        Deprecated.
        Clears this map.
        Specified by:
        clear in interface java.util.Map
        Overrides:
        clear in class AbstractHashedMap

      • entrySet

        public java.util.Set entrySet()
        Deprecated.
        Returns a set view of this map's entries. An iterator returned entry is valid until next() is called again. The setValue() method on the toArray entries has no effect.
        Specified by:
        entrySet in interface java.util.Map
        Overrides:
        entrySet in class AbstractHashedMap
        Returns:
        a set view of this map's entries

      • keySet

        public java.util.Set keySet()
        Deprecated.
        Returns a set view of this map's keys.
        Specified by:
        keySet in interface java.util.Map
        Overrides:
        keySet in class AbstractHashedMap
        Returns:
        a set view of this map's keys

      • values

        public java.util.Collection values()
        Deprecated.
        Returns a collection view of this map's values.
        Specified by:
        values in interface java.util.Map
        Overrides:
        values in class AbstractHashedMap
        Returns:
        a set view of this map's values