Package org.apache.commons.collections4.multimap

Class AbstractMultiValuedMap<K,​V>

  • Type Parameters:
    K - the type of the keys in this map
    V - the type of the values in this map
    All Implemented Interfaces:
    MultiValuedMap<K,​V>
    Direct Known Subclasses:
    AbstractListValuedMap, AbstractSetValuedMap
    public abstract class AbstractMultiValuedMap<K,​V>
extends Object
implements MultiValuedMap<K,​V>
    Abstract implementation of the MultiValuedMap interface to simplify the creation of subclass implementations.

    Subclasses specify a Map implementation to use as the internal storage.

    Since:
    4.1

    • Constructor Detail

      • AbstractMultiValuedMap

        protected AbstractMultiValuedMap()
        Constructor needed for subclass serialisation.

      • AbstractMultiValuedMap

        protected AbstractMultiValuedMap​(Map<K,​? extends Collection<V>> map)
        Constructor that wraps (not copies).
        Parameters:
        map - the map to wrap, must not be null
        Throws:
        NullPointerException - if the map is null

    • Method Detail

      • getMap

        protected Map<K,​? extends Collection<V>> getMap()
        Gets the map being wrapped.
        Returns:
        the wrapped map

      • setMap

        protected void setMap​(Map<K,​? extends Collection<V>> map)
        Sets the map being wrapped.

        NOTE: this method should only be used during deserialization

        Parameters:
        map - the map to wrap

      • createCollection

        protected abstract Collection<V> createCollection()

      • containsKey

        public boolean containsKey​(Object key)
        Description copied from interface: MultiValuedMap
        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 MultiValuedMap<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​(Object value)
        Description copied from interface: MultiValuedMap
        Checks whether the map contains at least one mapping for the specified value.
        Specified by:
        containsValue in interface MultiValuedMap<K,​V>
        Parameters:
        value - the value to search for
        Returns:
        true if the map contains the value

      • containsMapping

        public boolean containsMapping​(Object key,
                               Object value)
        Description copied from interface: MultiValuedMap
        Checks whether the map contains a mapping for the specified key and value.
        Specified by:
        containsMapping in interface MultiValuedMap<K,​V>
        Parameters:
        key - the key to search for
        value - the value to search for
        Returns:
        true if the map contains the value

      • entries

        public Collection<Map.Entry<K,​V>> entries()
        Description copied from interface: MultiValuedMap
        Returns a Collection view of the mappings contained in this multi-valued map.

        The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa.

        Specified by:
        entries in interface MultiValuedMap<K,​V>
        Returns:
        a set view of the mappings contained in this map

      • get

        public Collection<V> get​(K key)
        Gets the collection of values associated with the specified key. This would return an empty collection in case the mapping is not present
        Specified by:
        get in interface MultiValuedMap<K,​V>
        Parameters:
        key - the key to retrieve
        Returns:
        the Collection of values, will return an empty Collection for no mapping

      • remove

        public Collection<V> remove​(Object key)
        Removes all values associated with the specified key.

        A subsequent get(Object) would return an empty collection.

        Specified by:
        remove in interface MultiValuedMap<K,​V>
        Parameters:
        key - the key to remove values from
        Returns:
        the Collection of values removed, will return an empty, unmodifiable collection for no mapping found

      • removeMapping

        public boolean removeMapping​(Object key,
                             Object value)
        Removes a specific key/value mapping from the multi-valued map.

        The value 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, an empty collection would be returned from a subsequent get(Object).

        Specified by:
        removeMapping in interface MultiValuedMap<K,​V>
        Parameters:
        key - the key to remove from
        value - the value to remove
        Returns:
        true if the mapping was removed, false otherwise

      • isEmpty

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

      • keySet

        public Set<K> keySet()
        Description copied from interface: MultiValuedMap
        Returns a Set view of the keys contained in this multi-valued 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 result of the iteration is 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 MultiValuedMap<K,​V>
        Returns:
        a set view of the keys contained in this map

      • size

        public int size()
        Gets the total size of the map.

        Implementations would return the total size of the map which is the count of the values from all keys.

        This implementation does not cache the total size of the multi-valued map, but rather calculates it by iterating over the entries of the underlying map.

        Specified by:
        size in interface MultiValuedMap<K,​V>
        Returns:
        the total size of the map

      • values

        public Collection<V> values()
        Gets a collection containing all the values in the map.

        Returns a collection containing all the values from all keys.

        Specified by:
        values in interface MultiValuedMap<K,​V>
        Returns:
        a collection view of the values contained in this map

      • clear

        public void clear()
        Description copied from interface: MultiValuedMap
        Removes all of the mappings from this map (optional operation).

        The map will be empty after this call returns.

        Specified by:
        clear in interface MultiValuedMap<K,​V>

      • put

        public boolean put​(K key,
                   V 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 MultiValuedMap<K,​V>
        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 boolean putAll​(Map<? extends K,​? extends V> map)
        Copies all of the mappings from the specified map to this map. The effect of this call is equivalent to that of calling put(k, v) on this map once for each mapping from key k to value v in the specified map. The behavior of this operation is undefined if the specified map is modified while the operation is in progress.
        Specified by:
        putAll in interface MultiValuedMap<K,​V>
        Parameters:
        map - mappings to be stored in this map, may not be null
        Returns:
        true if the map changed as a result of this operation
        Throws:
        NullPointerException - if map is null

      • putAll

        public boolean putAll​(MultiValuedMap<? extends K,​? extends V> map)
        Copies all of the mappings from the specified MultiValuedMap to this map. The effect of this call is equivalent to that of calling put(k, v) on this map once for each mapping from key k to value v in the specified map. The behavior of this operation is undefined if the specified map is modified while the operation is in progress.
        Specified by:
        putAll in interface MultiValuedMap<K,​V>
        Parameters:
        map - mappings to be stored in this map, may not be null
        Returns:
        true if the map changed as a result of this operation
        Throws:
        NullPointerException - if map is null

      • keys

        public MultiSet<K> keys()
        Returns a MultiSet view of the key mapping contained in this map.

        Returns a MultiSet of keys with its values count as the count of the MultiSet. This multiset is backed by the map, so any changes in the map is reflected here. Any method which modifies this multiset like add, remove, Iterator.remove() etc throws UnsupportedOperationException.

        Specified by:
        keys in interface MultiValuedMap<K,​V>
        Returns:
        a bag view of the key mapping contained in this map

      • asMap

        public Map<K,​Collection<V>> asMap()
        Description copied from interface: MultiValuedMap
        Returns a view of this multi-valued map as a Map from each distinct key to the non-empty collection of that key's associated values.

        Note that this.asMap().get(k) is equivalent to this.get(k) only when k is a key contained in the multi-valued map; otherwise it returns null as opposed to an empty collection.

        Changes to the returned map or the collections that serve as its values will update the underlying multi-valued map, and vice versa. The map does not support put or putAll, nor do its entries support setValue.

        Specified by:
        asMap in interface MultiValuedMap<K,​V>
        Returns:
        a map view of the mappings in this multi-valued map

      • putAll

        public boolean putAll​(K key,
                      Iterable<? extends V> values)
        Adds Iterable values to the collection associated with the specified key.
        Specified by:
        putAll in interface MultiValuedMap<K,​V>
        Parameters:
        key - the key to store against
        values - the values to add to the collection at the key, may not be null
        Returns:
        true if this map changed
        Throws:
        NullPointerException - if values is null

      • mapIterator

        public MapIterator<K,​V> mapIterator()
        Description copied from interface: MultiValuedMap
        Obtains a MapIterator over this multi-valued map.

        A map iterator is an efficient way of iterating over maps. There is no need to access the entries collection or use Map.Entry objects.

        Specified by:
        mapIterator in interface MultiValuedMap<K,​V>
        Returns:
        a map iterator

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class Object

      • doWriteObject

        protected void doWriteObject​(ObjectOutputStream out)
                      throws IOException
        Write the map out using a custom routine.
        Parameters:
        out - the output stream
        Throws:
        IOException - any of the usual I/O related exceptions