Package org.apache.commons.collections.map

Class MultiValueMap

  • All Implemented Interfaces:
    java.util.Map, MultiMap
    public class MultiValueMap
extends AbstractMapDecorator
implements MultiMap
    A MultiValueMap decorates another map, allowing it to have more than one value for a key.

    A MultiMap is a Map with slightly different semantics. Putting a value into the map will add the value to a Collection at that key. Getting a value will return a Collection, holding all the values put to that key.

    This implementation is a decorator, allowing any Map implementation to be used as the base.

    In addition, this implementation allows the type of collection used for the values to be controlled. By default, an ArrayList is used, however a Class to instantiate may be specified, or a factory that returns a Collection instance.

    Note that MultiValueMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. This class may throw exceptions when accessed by concurrent threads without synchronization.

    Since:
    Commons Collections 3.2

    • Nested Class Summary

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

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

    • Constructor Summary

      Constructors 
      Constructor Description
      MultiValueMap()
      Creates a MultiValueMap based on a HashMap and storing the multiple values in an ArrayList.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void clear()
      Clear the map.
      boolean containsValue​(java.lang.Object value)
      Checks whether the map contains the value specified.
      boolean containsValue​(java.lang.Object key, java.lang.Object value)
      Checks whether the collection at the specified key contains the value.
      static MultiValueMap decorate​(java.util.Map map)
      Creates a map which wraps the given map and maps keys to ArrayLists.
      static MultiValueMap decorate​(java.util.Map map, java.lang.Class collectionClass)
      Creates a map which decorates the given map and maps keys to collections of type collectionClass.
      static MultiValueMap decorate​(java.util.Map map, Factory collectionFactory)
      Creates a map which decorates the given map and creates the value collections using the supplied collectionFactory.
      java.util.Collection getCollection​(java.lang.Object key)
      Gets the collection mapped to the specified key.
      java.util.Iterator iterator​(java.lang.Object key)
      Gets an iterator for the collection mapped to the specified key.
      java.lang.Object put​(java.lang.Object key, java.lang.Object value)
      Adds the value to the collection associated with the specified key.
      boolean putAll​(java.lang.Object key, java.util.Collection values)
      Adds a collection of values to the collection associated with the specified key.
      void putAll​(java.util.Map map)
      Override superclass to ensure that MultiMap instances are correctly handled.
      java.lang.Object remove​(java.lang.Object key, java.lang.Object value)
      Removes a specific value from map.
      int size​(java.lang.Object key)
      Gets the size of the collection mapped to the specified key.
      int totalSize()
      Gets the total size of the map by counting all the values.
      java.util.Collection values()
      Gets a collection containing all the values in the map.

      • Methods inherited from class java.lang.Object

        getClass, notify, notifyAll, wait, wait, wait

      • Methods inherited from interface java.util.Map

        compute, computeIfAbsent, computeIfPresent, containsKey, entrySet, equals, forEach, getOrDefault, hashCode, isEmpty, keySet, merge, putIfAbsent, replace, replace, replaceAll

    • Constructor Detail

      • MultiValueMap

        public MultiValueMap()
        Creates a MultiValueMap based on a HashMap and storing the multiple values in an ArrayList.

    • Method Detail

      • decorate

        public static MultiValueMap decorate​(java.util.Map map)
        Creates a map which wraps the given map and maps keys to ArrayLists.
        Parameters:
        map - the map to wrap

      • decorate

        public static MultiValueMap decorate​(java.util.Map map,
                                     java.lang.Class collectionClass)
        Creates a map which decorates the given map and maps keys to collections of type collectionClass.
        Parameters:
        map - the map to wrap
        collectionClass - the type of the collection class

      • decorate

        public static MultiValueMap decorate​(java.util.Map map,
                                     Factory collectionFactory)
        Creates a map which decorates the given map and creates the value collections using the supplied collectionFactory.
        Parameters:
        map - the map to decorate
        collectionFactory - the collection factory (must return a Collection object).

      • clear

        public void clear()
        Clear the map.
        Specified by:
        clear in interface java.util.Map
        Overrides:
        clear in class AbstractMapDecorator

      • remove

        public java.lang.Object remove​(java.lang.Object key,
                               java.lang.Object value)
        Removes a specific value from map.

        The item is removed from the collection mapped to the specified key. Other values attached to that key are unaffected.

        If the last value for a key is removed, null will be returned from a subsequant get(key).

        Specified by:
        remove in interface java.util.Map
        Specified by:
        remove in interface MultiMap
        Parameters:
        key - the key to remove from
        value - the value to remove
        Returns:
        the value removed (which was passed in), null if nothing removed

      • containsValue

        public boolean containsValue​(java.lang.Object value)
        Checks whether the map contains the value specified.

        This checks all collections against all keys for the value, and thus could be slow.

        Specified by:
        containsValue in interface java.util.Map
        Specified by:
        containsValue in interface MultiMap
        Overrides:
        containsValue in class AbstractMapDecorator
        Parameters:
        value - the value to search for
        Returns:
        true if the map contains the value

      • put

        public java.lang.Object put​(java.lang.Object key,
                            java.lang.Object value)
        Adds the value to the collection associated with the specified key.

        Unlike a normal Map the previous value is not replaced. Instead the new value is added to the collection stored against the key.

        Specified by:
        put in interface java.util.Map
        Specified by:
        put in interface MultiMap
        Overrides:
        put in class AbstractMapDecorator
        Parameters:
        key - the key to store against
        value - the value to add to the collection at the key
        Returns:
        the value added if the map changed and null if the map did not change

      • putAll

        public void putAll​(java.util.Map map)
        Override superclass to ensure that MultiMap instances are correctly handled.

        If you call this method with a normal map, each entry is added using put(Object,Object). If you call this method with a multi map, each entry is added using putAll(Object,Collection).

        Specified by:
        putAll in interface java.util.Map
        Overrides:
        putAll in class AbstractMapDecorator
        Parameters:
        map - the map to copy (either a normal or multi map)

      • values

        public java.util.Collection values()
        Gets a collection containing all the values in the map.

        This returns a collection containing the combination of values from all keys.

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

      • containsValue

        public boolean containsValue​(java.lang.Object key,
                             java.lang.Object value)
        Checks whether the collection at the specified key contains the value.
        Parameters:
        value - the value to search for
        Returns:
        true if the map contains the value

      • getCollection

        public java.util.Collection getCollection​(java.lang.Object key)
        Gets the collection mapped to the specified key. This method is a convenience method to typecast the result of get(key).
        Parameters:
        key - the key to retrieve
        Returns:
        the collection mapped to the key, null if no mapping

      • size

        public int size​(java.lang.Object key)
        Gets the size of the collection mapped to the specified key.
        Parameters:
        key - the key to get size for
        Returns:
        the size of the collection at the key, zero if key not in map

      • putAll

        public boolean putAll​(java.lang.Object key,
                      java.util.Collection values)
        Adds a collection of values to the collection associated with the specified key.
        Parameters:
        key - the key to store against
        values - the values to add to the collection at the key, null ignored
        Returns:
        true if this map changed

      • iterator

        public java.util.Iterator iterator​(java.lang.Object key)
        Gets an iterator for the collection mapped to the specified key.
        Parameters:
        key - the key to get an iterator for
        Returns:
        the iterator of the collection at the key, empty iterator if key not in map

      • totalSize

        public int totalSize()
        Gets the total size of the map by counting all the values.
        Returns:
        the total size of the map counting all values