Field Detail

• EMPTY_MULTI_VALUED_MAP

  public static final MultiValuedMap EMPTY_MULTI_VALUED_MAP

  An empty UnmodifiableMultiValuedMap.

Method Detail

• emptyMultiValuedMap

  public static <K,V> MultiValuedMap<K,V> emptyMultiValuedMap()

  Returns immutable EMPTY_MULTI_VALUED_MAP with generic type safety.

  Type Parameters:

  K - the type of key in the map

  V - the type of value in the map

  Returns:

  immutable and empty MultiValuedMap

• emptyIfNull

  public static <K,V> MultiValuedMap<K,V> emptyIfNull(MultiValuedMap<K,V> map)

  Returns an immutable empty MultiValuedMap if the argument is null, or the argument itself otherwise.

  Type Parameters:

  K - the type of key in the map

  V - the type of value in the map

  Parameters:

  map - the map, may be null

  Returns:

  an empty MultiValuedMap if the argument is null

• isEmpty

  public static boolean isEmpty(MultiValuedMap<?,?> map)

  Null-safe check if the specified MultiValuedMap is empty.

  If the provided map is null, returns true.

  Parameters:

  map - the map to check, may be null

  Returns:

  true if the map is empty or null

• getCollection

  public static <K,V> Collection<V> getCollection(MultiValuedMap<K,V> map,
                                                  K key)

  Gets a Collection from MultiValuedMap in a null-safe manner.

  Type Parameters:

  K - the key type

  V - the value type

  Parameters:

  map - the MultiValuedMap to use

  key - the key to look up

  Returns:

  the Collection in the MultiValuedMap, or null if input map is null

• getValuesAsList

  public static <K,V> List<V> getValuesAsList(MultiValuedMap<K,V> map,
                                              K key)

  Gets a List from MultiValuedMap in a null-safe manner.

  Type Parameters:

  K - the key type

  V - the value type

  Parameters:

  map - the MultiValuedMap to use

  key - the key to look up

  Returns:

  the Collection in the MultiValuedMap as List, or null if input map is null

• getValuesAsSet

  public static <K,V> Set<V> getValuesAsSet(MultiValuedMap<K,V> map,
                                            K key)

  Gets a Set from MultiValuedMap in a null-safe manner.

  Type Parameters:

  K - the key type

  V - the value type

  Parameters:

  map - the MultiValuedMap to use

  key - the key to look up

  Returns:

  the Collection in the MultiValuedMap as Set, or null if input map is null

• getValuesAsBag

  public static <K,V> Bag<V> getValuesAsBag(MultiValuedMap<K,V> map,
                                            K key)

  Gets a Bag from MultiValuedMap in a null-safe manner.

  Type Parameters:

  K - the key type

  V - the value type

  Parameters:

  map - the MultiValuedMap to use

  key - the key to look up

  Returns:

  the Collection in the MultiValuedMap as Bag, or null if input map is null

• newListValuedHashMap

  public static <K,V> ListValuedMap<K,V> newListValuedHashMap()

  Creates a ListValuedMap with an ArrayList as collection class to store the values mapped to a key.

  Type Parameters:

  K - the key type

  V - the value type

  Returns:

  a new ListValuedMap

• newSetValuedHashMap

  public static <K,V> SetValuedMap<K,V> newSetValuedHashMap()

  Creates a SetValuedMap with an HashSet as collection class to store the values mapped to a key.

  Type Parameters:

  K - the key type

  V - the value type

  Returns:

  a new SetValuedMap

• unmodifiableMultiValuedMap

  public static <K,V> MultiValuedMap<K,V> unmodifiableMultiValuedMap(MultiValuedMap<? extends K,? extends V> map)

  Returns an UnmodifiableMultiValuedMap backed by the given map.

  Type Parameters:

  K - the key type

  V - the value type

  Parameters:

  map - the MultiValuedMap to decorate, must not be null

  Returns:

  an unmodifiable MultiValuedMap backed by the provided map

  Throws:

  NullPointerException - if map is null

• transformedMultiValuedMap

  public static <K,V> MultiValuedMap<K,V> transformedMultiValuedMap(MultiValuedMap<K,V> map,
                                                                    Transformer<? super K,? extends K> keyTransformer,
                                                                    Transformer<? super V,? extends V> valueTransformer)

  Returns a TransformedMultiValuedMap backed by the given map.

  This method returns a new MultiValuedMap (decorating the specified map) that will transform any new entries added to it. Existing entries in the specified map will not be transformed. If you want that behaviour, see TransformedMultiValuedMap.transformedMap(org.apache.commons.collections4.MultiValuedMap<K, V>, org.apache.commons.collections4.Transformer<? super K, ? extends K>, org.apache.commons.collections4.Transformer<? super V, ? extends V>).

  Each object is passed through the transformers as it is added to the Map. It is important not to use the original map after invoking this method, as it is a back door for adding untransformed objects.

  If there are any elements already in the map being decorated, they are NOT transformed.

  Type Parameters:

  K - the key type

  V - the value type

  Parameters:

  map - the MultiValuedMap to transform, must not be null, typically empty

  keyTransformer - the transformer for the map keys, null means no transformation

  valueTransformer - the transformer for the map values, null means no transformation

  Returns:

  a transformed MultiValuedMap backed by the given map

  Throws:

  NullPointerException - if map is null