@GwtCompatible(emulated=true) public final class Multimaps extends Object
Multimap
.
See the Guava User Guide article on
Multimaps
.
Modifier and Type | Method and Description |
---|---|
static <K,V> Map<K,List<V>> |
asMap(ListMultimap<K,V> multimap)
|
static <K,V> Map<K,Collection<V>> |
asMap(Multimap<K,V> multimap)
Returns
multimap.asMap() . |
static <K,V> Map<K,Set<V>> |
asMap(SetMultimap<K,V> multimap)
|
static <K,V> Map<K,SortedSet<V>> |
asMap(SortedSetMultimap<K,V> multimap)
Returns
multimap.asMap() , with its type
corrected from Map<K, Collection<V>> to
Map<K, SortedSet<V>> . |
static <K,V> Multimap<K,V> |
filterEntries(Multimap<K,V> unfiltered,
Predicate<? super Map.Entry<K,V>> entryPredicate)
Returns a multimap containing the mappings in
unfiltered that
satisfy a predicate. |
static <K,V> SetMultimap<K,V> |
filterEntries(SetMultimap<K,V> unfiltered,
Predicate<? super Map.Entry<K,V>> entryPredicate)
Returns a multimap containing the mappings in
unfiltered that
satisfy a predicate. |
static <K,V> ListMultimap<K,V> |
filterKeys(ListMultimap<K,V> unfiltered,
Predicate<? super K> keyPredicate)
Returns a multimap containing the mappings in
unfiltered whose keys
satisfy a predicate. |
static <K,V> Multimap<K,V> |
filterKeys(Multimap<K,V> unfiltered,
Predicate<? super K> keyPredicate)
Returns a multimap containing the mappings in
unfiltered whose keys
satisfy a predicate. |
static <K,V> SetMultimap<K,V> |
filterKeys(SetMultimap<K,V> unfiltered,
Predicate<? super K> keyPredicate)
Returns a multimap containing the mappings in
unfiltered whose keys
satisfy a predicate. |
static <K,V> Multimap<K,V> |
filterValues(Multimap<K,V> unfiltered,
Predicate<? super V> valuePredicate)
Returns a multimap containing the mappings in
unfiltered whose values
satisfy a predicate. |
static <K,V> SetMultimap<K,V> |
filterValues(SetMultimap<K,V> unfiltered,
Predicate<? super V> valuePredicate)
Returns a multimap containing the mappings in
unfiltered whose values
satisfy a predicate. |
static <T,K,V,M extends Multimap<K,V>> |
flatteningToMultimap(Function<? super T,? extends K> keyFunction,
Function<? super T,? extends Stream<? extends V>> valueFunction,
Supplier<M> multimapSupplier)
Returns a
Collector accumulating entries into a Multimap generated from the
specified supplier. |
static <K,V> SetMultimap<K,V> |
forMap(Map<K,V> map)
Returns a multimap view of the specified map.
|
static <K,V> ImmutableListMultimap<K,V> |
index(Iterable<V> values,
Function<? super V,K> keyFunction)
Creates an index
ImmutableListMultimap that contains the results of
applying a specified function to each item in an Iterable of
values. |
static <K,V> ImmutableListMultimap<K,V> |
index(Iterator<V> values,
Function<? super V,K> keyFunction)
Creates an index
ImmutableListMultimap that contains the results of
applying a specified function to each item in an Iterator of
values. |
static <K,V,M extends Multimap<K,V>> |
invertFrom(Multimap<? extends V,? extends K> source,
M dest)
Copies each key-value mapping in
source into dest , with
its key and value reversed. |
static <K,V> ListMultimap<K,V> |
newListMultimap(Map<K,Collection<V>> map,
Supplier<? extends List<V>> factory)
Creates a new
ListMultimap that uses the provided map and factory. |
static <K,V> Multimap<K,V> |
newMultimap(Map<K,Collection<V>> map,
Supplier<? extends Collection<V>> factory)
Creates a new
Multimap backed by map , whose internal value collections are
generated by factory . |
static <K,V> SetMultimap<K,V> |
newSetMultimap(Map<K,Collection<V>> map,
Supplier<? extends Set<V>> factory)
Creates a new
SetMultimap that uses the provided map and factory. |
static <K,V> SortedSetMultimap<K,V> |
newSortedSetMultimap(Map<K,Collection<V>> map,
Supplier<? extends SortedSet<V>> factory)
Creates a new
SortedSetMultimap that uses the provided map and
factory. |
static <K,V> ListMultimap<K,V> |
synchronizedListMultimap(ListMultimap<K,V> multimap)
Returns a synchronized (thread-safe)
ListMultimap backed by the
specified multimap. |
static <K,V> Multimap<K,V> |
synchronizedMultimap(Multimap<K,V> multimap)
Returns a synchronized (thread-safe) multimap backed by the specified
multimap.
|
static <K,V> SetMultimap<K,V> |
synchronizedSetMultimap(SetMultimap<K,V> multimap)
Returns a synchronized (thread-safe)
SetMultimap backed by the
specified multimap. |
static <K,V> SortedSetMultimap<K,V> |
synchronizedSortedSetMultimap(SortedSetMultimap<K,V> multimap)
Returns a synchronized (thread-safe)
SortedSetMultimap backed by
the specified multimap. |
static <T,K,V,M extends Multimap<K,V>> |
toMultimap(Function<? super T,? extends K> keyFunction,
Function<? super T,? extends V> valueFunction,
Supplier<M> multimapSupplier)
Returns a
Collector accumulating entries into a Multimap generated from the
specified supplier. |
static <K,V1,V2> ListMultimap<K,V2> |
transformEntries(ListMultimap<K,V1> fromMap,
Maps.EntryTransformer<? super K,? super V1,V2> transformer)
Returns a view of a
ListMultimap whose values are derived from the
original multimap's entries. |
static <K,V1,V2> Multimap<K,V2> |
transformEntries(Multimap<K,V1> fromMap,
Maps.EntryTransformer<? super K,? super V1,V2> transformer)
Returns a view of a multimap whose values are derived from the original
multimap's entries.
|
static <K,V1,V2> ListMultimap<K,V2> |
transformValues(ListMultimap<K,V1> fromMultimap,
Function<? super V1,V2> function)
Returns a view of a
ListMultimap where each value is transformed by
a function. |
static <K,V1,V2> Multimap<K,V2> |
transformValues(Multimap<K,V1> fromMultimap,
Function<? super V1,V2> function)
Returns a view of a multimap where each value is transformed by a function.
|
static <K,V> ListMultimap<K,V> |
unmodifiableListMultimap(ImmutableListMultimap<K,V> delegate)
Deprecated.
no need to use this
|
static <K,V> ListMultimap<K,V> |
unmodifiableListMultimap(ListMultimap<K,V> delegate)
Returns an unmodifiable view of the specified
ListMultimap . |
static <K,V> Multimap<K,V> |
unmodifiableMultimap(ImmutableMultimap<K,V> delegate)
Deprecated.
no need to use this
|
static <K,V> Multimap<K,V> |
unmodifiableMultimap(Multimap<K,V> delegate)
Returns an unmodifiable view of the specified multimap.
|
static <K,V> SetMultimap<K,V> |
unmodifiableSetMultimap(ImmutableSetMultimap<K,V> delegate)
Deprecated.
no need to use this
|
static <K,V> SetMultimap<K,V> |
unmodifiableSetMultimap(SetMultimap<K,V> delegate)
Returns an unmodifiable view of the specified
SetMultimap . |
static <K,V> SortedSetMultimap<K,V> |
unmodifiableSortedSetMultimap(SortedSetMultimap<K,V> delegate)
Returns an unmodifiable view of the specified
SortedSetMultimap . |
@Beta public static <T,K,V,M extends Multimap<K,V>> Collector<T,?,M> toMultimap(Function<? super T,? extends K> keyFunction, Function<? super T,? extends V> valueFunction, Supplier<M> multimapSupplier)
Collector
accumulating entries into a Multimap
generated from the
specified supplier. The keys and values of the entries are the result of applying the provided
mapping functions to the input elements, accumulated in the encounter order of the stream.
Example:
static final ListMultimap<Character, String> FIRST_LETTER_MULTIMAP =
Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
.collect(
toMultimap(
str -> str.charAt(0),
str -> str.substring(1),
MultimapBuilder.treeKeys().arrayListValues()::build));
// is equivalent to
static final ListMultimap<Character, String> FIRST_LETTER_MULTIMAP;
static {
FIRST_LETTER_MULTIMAP = MultimapBuilder.treeKeys().arrayListValues().build();
FIRST_LETTER_MULTIMAP.put('b', "anana");
FIRST_LETTER_MULTIMAP.put('a', "pple");
FIRST_LETTER_MULTIMAP.put('a', "sparagus");
FIRST_LETTER_MULTIMAP.put('c', "arrot");
FIRST_LETTER_MULTIMAP.put('c', "herry");
}
@Beta public static <T,K,V,M extends Multimap<K,V>> Collector<T,?,M> flatteningToMultimap(Function<? super T,? extends K> keyFunction, Function<? super T,? extends Stream<? extends V>> valueFunction, Supplier<M> multimapSupplier)
Collector
accumulating entries into a Multimap
generated from the
specified supplier. Each input element is mapped to a key and a stream of values, each of which
are put into the resulting Multimap
, in the encounter order of the stream and the
encounter order of the streams of values.
Example:
static final ListMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
.collect(
flatteningToMultimap(
str -> str.charAt(0),
str -> str.substring(1).chars().mapToObj(c -> (char) c),
MultimapBuilder.linkedHashKeys().arrayListValues()::build));
// is equivalent to
static final ListMultimap<Character, Character> FIRST_LETTER_MULTIMAP;
static {
FIRST_LETTER_MULTIMAP = MultimapBuilder.linkedHashKeys().arrayListValues().build();
FIRST_LETTER_MULTIMAP.putAll('b', Arrays.asList('a', 'n', 'a', 'n', 'a'));
FIRST_LETTER_MULTIMAP.putAll('a', Arrays.asList('p', 'p', 'l', 'e'));
FIRST_LETTER_MULTIMAP.putAll('c', Arrays.asList('a', 'r', 'r', 'o', 't'));
FIRST_LETTER_MULTIMAP.putAll('a', Arrays.asList('s', 'p', 'a', 'r', 'a', 'g', 'u', 's'));
FIRST_LETTER_MULTIMAP.putAll('c', Arrays.asList('h', 'e', 'r', 'r', 'y'));
}
public static <K,V> Multimap<K,V> newMultimap(Map<K,Collection<V>> map, Supplier<? extends Collection<V>> factory)
Multimap
backed by map
, whose internal value collections are
generated by factory
.
Warning: do not use this method when the collections returned by factory
implement either List
or Set
! Use the more specific method newListMultimap(java.util.Map<K, java.util.Collection<V>>, com.google.common.base.Supplier<? extends java.util.List<V>>)
, newSetMultimap(java.util.Map<K, java.util.Collection<V>>, com.google.common.base.Supplier<? extends java.util.Set<V>>)
or newSortedSetMultimap(java.util.Map<K, java.util.Collection<V>>, com.google.common.base.Supplier<? extends java.util.SortedSet<V>>)
instead, to avoid
very surprising behavior from Multimap.equals(java.lang.Object)
.
The factory
-generated and map
classes determine the multimap iteration
order. They also specify the behavior of the equals
, hashCode
, and toString
methods for the multimap and its returned views. However, the multimap's get
method returns instances of a different class than factory.get()
does.
The multimap is serializable if map
, factory
, the collections generated by
factory
, and the multimap contents are all serializable.
The multimap is not threadsafe when any concurrent operations update the multimap, even if
map
and the instances generated by factory
are. Concurrent read operations will
work correctly. To allow concurrent update operations, wrap the multimap with a call to synchronizedMultimap(com.google.common.collect.Multimap<K, V>)
.
Call this method only when the simpler methods ArrayListMultimap.create()
, HashMultimap.create()
, LinkedHashMultimap.create()
, LinkedListMultimap.create()
, TreeMultimap.create()
, and TreeMultimap.create(Comparator, Comparator)
won't suffice.
Note: the multimap assumes complete ownership over of map
and the collections
returned by factory
. Those objects should not be manually updated and they should not
use soft, weak, or phantom references.
map
- place to store the mapping from each key to its corresponding valuesfactory
- supplier of new, empty collections that will each hold all values for a given
keyIllegalArgumentException
- if map
is not emptypublic static <K,V> ListMultimap<K,V> newListMultimap(Map<K,Collection<V>> map, Supplier<? extends List<V>> factory)
ListMultimap
that uses the provided map and factory.
It can generate a multimap based on arbitrary Map
and List
classes.
The factory
-generated and map
classes determine the
multimap iteration order. They also specify the behavior of the
equals
, hashCode
, and toString
methods for the
multimap and its returned views. The multimap's get
, removeAll
, and replaceValues
methods return RandomAccess
lists if the factory does. However, the multimap's get
method
returns instances of a different class than does factory.get()
.
The multimap is serializable if map
, factory
, the
lists generated by factory
, and the multimap contents are all
serializable.
The multimap is not threadsafe when any concurrent operations update the
multimap, even if map
and the instances generated by
factory
are. Concurrent read operations will work correctly. To
allow concurrent update operations, wrap the multimap with a call to
synchronizedListMultimap(com.google.common.collect.ListMultimap<K, V>)
.
Call this method only when the simpler methods
ArrayListMultimap.create()
and LinkedListMultimap.create()
won't suffice.
Note: the multimap assumes complete ownership over of map
and
the lists returned by factory
. Those objects should not be manually
updated, they should be empty when provided, and they should not use soft,
weak, or phantom references.
map
- place to store the mapping from each key to its corresponding
valuesfactory
- supplier of new, empty lists that will each hold all values
for a given keyIllegalArgumentException
- if map
is not emptypublic static <K,V> SetMultimap<K,V> newSetMultimap(Map<K,Collection<V>> map, Supplier<? extends Set<V>> factory)
SetMultimap
that uses the provided map and factory.
It can generate a multimap based on arbitrary Map
and Set
classes.
The factory
-generated and map
classes determine the
multimap iteration order. They also specify the behavior of the
equals
, hashCode
, and toString
methods for the
multimap and its returned views. However, the multimap's get
method returns instances of a different class than factory.get()
does.
The multimap is serializable if map
, factory
, the
sets generated by factory
, and the multimap contents are all
serializable.
The multimap is not threadsafe when any concurrent operations update the
multimap, even if map
and the instances generated by
factory
are. Concurrent read operations will work correctly. To
allow concurrent update operations, wrap the multimap with a call to
synchronizedSetMultimap(com.google.common.collect.SetMultimap<K, V>)
.
Call this method only when the simpler methods
HashMultimap.create()
, LinkedHashMultimap.create()
,
TreeMultimap.create()
, and
TreeMultimap.create(Comparator, Comparator)
won't suffice.
Note: the multimap assumes complete ownership over of map
and
the sets returned by factory
. Those objects should not be manually
updated and they should not use soft, weak, or phantom references.
map
- place to store the mapping from each key to its corresponding
valuesfactory
- supplier of new, empty sets that will each hold all values
for a given keyIllegalArgumentException
- if map
is not emptypublic static <K,V> SortedSetMultimap<K,V> newSortedSetMultimap(Map<K,Collection<V>> map, Supplier<? extends SortedSet<V>> factory)
SortedSetMultimap
that uses the provided map and
factory. It can generate a multimap based on arbitrary Map
and
SortedSet
classes.
The factory
-generated and map
classes determine the
multimap iteration order. They also specify the behavior of the
equals
, hashCode
, and toString
methods for the
multimap and its returned views. However, the multimap's get
method returns instances of a different class than factory.get()
does.
The multimap is serializable if map
, factory
, the
sets generated by factory
, and the multimap contents are all
serializable.
The multimap is not threadsafe when any concurrent operations update the
multimap, even if map
and the instances generated by
factory
are. Concurrent read operations will work correctly. To
allow concurrent update operations, wrap the multimap with a call to
synchronizedSortedSetMultimap(com.google.common.collect.SortedSetMultimap<K, V>)
.
Call this method only when the simpler methods
TreeMultimap.create()
and
TreeMultimap.create(Comparator, Comparator)
won't suffice.
Note: the multimap assumes complete ownership over of map
and
the sets returned by factory
. Those objects should not be manually
updated and they should not use soft, weak, or phantom references.
map
- place to store the mapping from each key to its corresponding
valuesfactory
- supplier of new, empty sorted sets that will each hold
all values for a given keyIllegalArgumentException
- if map
is not emptypublic static <K,V,M extends Multimap<K,V>> M invertFrom(Multimap<? extends V,? extends K> source, M dest)
source
into dest
, with
its key and value reversed.
If source
is an ImmutableMultimap
, consider using
ImmutableMultimap.inverse()
instead.
source
- any multimapdest
- the multimap to copy into; usually emptydest
public static <K,V> Multimap<K,V> synchronizedMultimap(Multimap<K,V> multimap)
It is imperative that the user manually synchronize on the returned multimap when accessing any of its collection views:
Multimap<K, V> multimap = Multimaps.synchronizedMultimap(
HashMultimap.<K, V>create());
...
Collection<V> values = multimap.get(key); // Needn't be in synchronized block
...
synchronized (multimap) { // Synchronizing on multimap, not values!
Iterator<V> i = values.iterator(); // Must be in synchronized block
while (i.hasNext()) {
foo(i.next());
}
}
Failure to follow this advice may result in non-deterministic behavior.
Note that the generated multimap's Multimap.removeAll(java.lang.Object)
and
Multimap.replaceValues(K, java.lang.Iterable<? extends V>)
methods return collections that aren't
synchronized.
The returned multimap will be serializable if the specified multimap is serializable.
multimap
- the multimap to be wrapped in a synchronized viewpublic static <K,V> Multimap<K,V> unmodifiableMultimap(Multimap<K,V> delegate)
UnsupportedOperationException
.
Note that the generated multimap's Multimap.removeAll(java.lang.Object)
and
Multimap.replaceValues(K, java.lang.Iterable<? extends V>)
methods return collections that are
modifiable.
The returned multimap will be serializable if the specified multimap is serializable.
delegate
- the multimap for which an unmodifiable view is to be
returned@Deprecated public static <K,V> Multimap<K,V> unmodifiableMultimap(ImmutableMultimap<K,V> delegate)
public static <K,V> SetMultimap<K,V> synchronizedSetMultimap(SetMultimap<K,V> multimap)
SetMultimap
backed by the
specified multimap.
You must follow the warnings described in synchronizedMultimap(com.google.common.collect.Multimap<K, V>)
.
The returned multimap will be serializable if the specified multimap is serializable.
multimap
- the multimap to be wrappedpublic static <K,V> SetMultimap<K,V> unmodifiableSetMultimap(SetMultimap<K,V> delegate)
SetMultimap
. Query
operations on the returned multimap "read through" to the specified
multimap, and attempts to modify the returned multimap, either directly or
through the multimap's views, result in an
UnsupportedOperationException
.
Note that the generated multimap's Multimap.removeAll(java.lang.Object)
and
Multimap.replaceValues(K, java.lang.Iterable<? extends V>)
methods return collections that are
modifiable.
The returned multimap will be serializable if the specified multimap is serializable.
delegate
- the multimap for which an unmodifiable view is to be
returned@Deprecated public static <K,V> SetMultimap<K,V> unmodifiableSetMultimap(ImmutableSetMultimap<K,V> delegate)
public static <K,V> SortedSetMultimap<K,V> synchronizedSortedSetMultimap(SortedSetMultimap<K,V> multimap)
SortedSetMultimap
backed by
the specified multimap.
You must follow the warnings described in synchronizedMultimap(com.google.common.collect.Multimap<K, V>)
.
The returned multimap will be serializable if the specified multimap is serializable.
multimap
- the multimap to be wrappedpublic static <K,V> SortedSetMultimap<K,V> unmodifiableSortedSetMultimap(SortedSetMultimap<K,V> delegate)
SortedSetMultimap
.
Query operations on the returned multimap "read through" to the specified
multimap, and attempts to modify the returned multimap, either directly or
through the multimap's views, result in an
UnsupportedOperationException
.
Note that the generated multimap's Multimap.removeAll(java.lang.Object)
and
Multimap.replaceValues(K, java.lang.Iterable<? extends V>)
methods return collections that are
modifiable.
The returned multimap will be serializable if the specified multimap is serializable.
delegate
- the multimap for which an unmodifiable view is to be
returnedpublic static <K,V> ListMultimap<K,V> synchronizedListMultimap(ListMultimap<K,V> multimap)
ListMultimap
backed by the
specified multimap.
You must follow the warnings described in synchronizedMultimap(com.google.common.collect.Multimap<K, V>)
.
multimap
- the multimap to be wrappedpublic static <K,V> ListMultimap<K,V> unmodifiableListMultimap(ListMultimap<K,V> delegate)
ListMultimap
. Query
operations on the returned multimap "read through" to the specified
multimap, and attempts to modify the returned multimap, either directly or
through the multimap's views, result in an
UnsupportedOperationException
.
Note that the generated multimap's Multimap.removeAll(java.lang.Object)
and
Multimap.replaceValues(K, java.lang.Iterable<? extends V>)
methods return collections that are
modifiable.
The returned multimap will be serializable if the specified multimap is serializable.
delegate
- the multimap for which an unmodifiable view is to be
returned@Deprecated public static <K,V> ListMultimap<K,V> unmodifiableListMultimap(ImmutableListMultimap<K,V> delegate)
@Beta public static <K,V> Map<K,List<V>> asMap(ListMultimap<K,V> multimap)
@Beta public static <K,V> Map<K,Set<V>> asMap(SetMultimap<K,V> multimap)
@Beta public static <K,V> Map<K,SortedSet<V>> asMap(SortedSetMultimap<K,V> multimap)
multimap.asMap()
, with its type
corrected from Map<K, Collection<V>>
to
Map<K, SortedSet<V>>
.@Beta public static <K,V> Map<K,Collection<V>> asMap(Multimap<K,V> multimap)
multimap.asMap()
. This is provided for
parity with the other more strongly-typed asMap()
implementations.public static <K,V> SetMultimap<K,V> forMap(Map<K,V> map)
remove
operation, or through the setValue
operation on a map entry
returned by the iterator), the results of the iteration are undefined.
The multimap supports mapping removal, which removes the corresponding
mapping from the map. It does not support any operations which might add
mappings, such as put
, putAll
or replaceValues
.
The returned multimap will be serializable if the specified map is serializable.
map
- the backing map for the returned multimap viewpublic static <K,V1,V2> Multimap<K,V2> transformValues(Multimap<K,V1> fromMultimap, Function<? super V1,V2> function)
Multimap<String, Integer> multimap =
ImmutableSetMultimap.of("a", 2, "b", -3, "b", -3, "a", 4, "c", 6);
Function<Integer, String> square = new Function<Integer, String>() {
public String apply(Integer in) {
return Integer.toString(in * in);
}
};
Multimap<String, String> transformed =
Multimaps.transformValues(multimap, square);
System.out.println(transformed);
... prints {a=[4, 16], b=[9, 9], c=[36]}
.
Changes in the underlying multimap are reflected in this view. Conversely, this view supports removal operations, and these are reflected in the underlying multimap.
It's acceptable for the underlying multimap to contain null keys, and even null values provided that the function is capable of accepting null input. The transformed multimap might contain null values, if the function sometimes gives a null result.
The returned multimap is not thread-safe or serializable, even if the
underlying multimap is. The equals
and hashCode
methods
of the returned multimap are meaningless, since there is not a definition
of equals
or hashCode
for general collections, and
get()
will return a general Collection
as opposed to a
List
or a Set
.
The function is applied lazily, invoked when needed. This is necessary
for the returned multimap to be a view, but it means that the function will
be applied many times for bulk operations like
Multimap.containsValue(java.lang.Object)
and Multimap.toString()
. For this to
perform well, function
should be fast. To avoid lazy evaluation
when the returned multimap doesn't need to be a view, copy the returned
multimap into a new multimap of your choosing.
public static <K,V1,V2> Multimap<K,V2> transformEntries(Multimap<K,V1> fromMap, Maps.EntryTransformer<? super K,? super V1,V2> transformer)
transformValues(com.google.common.collect.Multimap<K, V1>, com.google.common.base.Function<? super V1, V2>)
, this method's
entry-transformation logic may depend on the key as well as the value.
All other properties of the transformed multimap, such as iteration order, are left intact. For example, the code:
SetMultimap<String, Integer> multimap =
ImmutableSetMultimap.of("a", 1, "a", 4, "b", -6);
EntryTransformer<String, Integer, String> transformer =
new EntryTransformer<String, Integer, String>() {
public String transformEntry(String key, Integer value) {
return (value >= 0) ? key : "no" + key;
}
};
Multimap<String, String> transformed =
Multimaps.transformEntries(multimap, transformer);
System.out.println(transformed);
... prints {a=[a, a], b=[nob]}
.
Changes in the underlying multimap are reflected in this view. Conversely, this view supports removal operations, and these are reflected in the underlying multimap.
It's acceptable for the underlying multimap to contain null keys and null values provided that the transformer is capable of accepting null inputs. The transformed multimap might contain null values if the transformer sometimes gives a null result.
The returned multimap is not thread-safe or serializable, even if the
underlying multimap is. The equals
and hashCode
methods
of the returned multimap are meaningless, since there is not a definition
of equals
or hashCode
for general collections, and
get()
will return a general Collection
as opposed to a
List
or a Set
.
The transformer is applied lazily, invoked when needed. This is
necessary for the returned multimap to be a view, but it means that the
transformer will be applied many times for bulk operations like Multimap.containsValue(java.lang.Object)
and Object.toString()
. For this to perform
well, transformer
should be fast. To avoid lazy evaluation when the
returned multimap doesn't need to be a view, copy the returned multimap
into a new multimap of your choosing.
Warning: This method assumes that for any instance k
of
EntryTransformer
key type K
, k.equals(k2)
implies
that k2
is also of type K
. Using an EntryTransformer
key type for which this may not hold, such as ArrayList
, may risk a ClassCastException
when calling methods on
the transformed multimap.
public static <K,V1,V2> ListMultimap<K,V2> transformValues(ListMultimap<K,V1> fromMultimap, Function<? super V1,V2> function)
ListMultimap
where each value is transformed by
a function. All other properties of the multimap, such as iteration order,
are left intact. For example, the code:
ListMultimap<String, Integer> multimap
= ImmutableListMultimap.of("a", 4, "a", 16, "b", 9);
Function<Integer, Double> sqrt =
new Function<Integer, Double>() {
public Double apply(Integer in) {
return Math.sqrt((int) in);
}
};
ListMultimap<String, Double> transformed = Multimaps.transformValues(map,
sqrt);
System.out.println(transformed);
... prints {a=[2.0, 4.0], b=[3.0]}
.
Changes in the underlying multimap are reflected in this view. Conversely, this view supports removal operations, and these are reflected in the underlying multimap.
It's acceptable for the underlying multimap to contain null keys, and even null values provided that the function is capable of accepting null input. The transformed multimap might contain null values, if the function sometimes gives a null result.
The returned multimap is not thread-safe or serializable, even if the underlying multimap is.
The function is applied lazily, invoked when needed. This is necessary
for the returned multimap to be a view, but it means that the function will
be applied many times for bulk operations like
Multimap.containsValue(java.lang.Object)
and Multimap.toString()
. For this to
perform well, function
should be fast. To avoid lazy evaluation
when the returned multimap doesn't need to be a view, copy the returned
multimap into a new multimap of your choosing.
public static <K,V1,V2> ListMultimap<K,V2> transformEntries(ListMultimap<K,V1> fromMap, Maps.EntryTransformer<? super K,? super V1,V2> transformer)
ListMultimap
whose values are derived from the
original multimap's entries. In contrast to
transformValues(ListMultimap, Function)
, this method's
entry-transformation logic may depend on the key as well as the value.
All other properties of the transformed multimap, such as iteration order, are left intact. For example, the code:
Multimap<String, Integer> multimap =
ImmutableMultimap.of("a", 1, "a", 4, "b", 6);
EntryTransformer<String, Integer, String> transformer =
new EntryTransformer<String, Integer, String>() {
public String transformEntry(String key, Integer value) {
return key + value;
}
};
Multimap<String, String> transformed =
Multimaps.transformEntries(multimap, transformer);
System.out.println(transformed);
... prints {"a"=["a1", "a4"], "b"=["b6"]}
.
Changes in the underlying multimap are reflected in this view. Conversely, this view supports removal operations, and these are reflected in the underlying multimap.
It's acceptable for the underlying multimap to contain null keys and null values provided that the transformer is capable of accepting null inputs. The transformed multimap might contain null values if the transformer sometimes gives a null result.
The returned multimap is not thread-safe or serializable, even if the underlying multimap is.
The transformer is applied lazily, invoked when needed. This is
necessary for the returned multimap to be a view, but it means that the
transformer will be applied many times for bulk operations like Multimap.containsValue(java.lang.Object)
and Object.toString()
. For this to perform
well, transformer
should be fast. To avoid lazy evaluation when the
returned multimap doesn't need to be a view, copy the returned multimap
into a new multimap of your choosing.
Warning: This method assumes that for any instance k
of
EntryTransformer
key type K
, k.equals(k2)
implies
that k2
is also of type K
. Using an EntryTransformer
key type for which this may not hold, such as ArrayList
, may risk a ClassCastException
when calling methods on
the transformed multimap.
public static <K,V> ImmutableListMultimap<K,V> index(Iterable<V> values, Function<? super V,K> keyFunction)
ImmutableListMultimap
that contains the results of
applying a specified function to each item in an Iterable
of
values. Each value will be stored as a value in the resulting multimap,
yielding a multimap with the same size as the input iterable. The key used
to store that value in the multimap will be the result of calling the
function on that value. The resulting multimap is created as an immutable
snapshot. In the returned multimap, keys appear in the order they are first
encountered, and the values corresponding to each key appear in the same
order as they are encountered.
For example,
List<String> badGuys =
Arrays.asList("Inky", "Blinky", "Pinky", "Pinky", "Clyde");
Function<String, Integer> stringLengthFunction = ...;
Multimap<Integer, String> index =
Multimaps.index(badGuys, stringLengthFunction);
System.out.println(index);
prints
{4=[Inky], 6=[Blinky], 5=[Pinky, Pinky, Clyde]}
The returned multimap is serializable if its keys and values are all serializable.
values
- the values to use when constructing the ImmutableListMultimap
keyFunction
- the function used to produce the key for each valueImmutableListMultimap
mapping the result of evaluating the
function keyFunction
on each value in the input collection to
that valueNullPointerException
- if any element of values
is null
, or if keyFunction
produces null
for any keypublic static <K,V> ImmutableListMultimap<K,V> index(Iterator<V> values, Function<? super V,K> keyFunction)
ImmutableListMultimap
that contains the results of
applying a specified function to each item in an Iterator
of
values. Each value will be stored as a value in the resulting multimap,
yielding a multimap with the same size as the input iterator. The key used
to store that value in the multimap will be the result of calling the
function on that value. The resulting multimap is created as an immutable
snapshot. In the returned multimap, keys appear in the order they are first
encountered, and the values corresponding to each key appear in the same
order as they are encountered.
For example,
List<String> badGuys =
Arrays.asList("Inky", "Blinky", "Pinky", "Pinky", "Clyde");
Function<String, Integer> stringLengthFunction = ...;
Multimap<Integer, String> index =
Multimaps.index(badGuys.iterator(), stringLengthFunction);
System.out.println(index);
prints
{4=[Inky], 6=[Blinky], 5=[Pinky, Pinky, Clyde]}
The returned multimap is serializable if its keys and values are all serializable.
values
- the values to use when constructing the ImmutableListMultimap
keyFunction
- the function used to produce the key for each valueImmutableListMultimap
mapping the result of evaluating the
function keyFunction
on each value in the input collection to
that valueNullPointerException
- if any element of values
is null
, or if keyFunction
produces null
for any keypublic static <K,V> Multimap<K,V> filterKeys(Multimap<K,V> unfiltered, Predicate<? super K> keyPredicate)
unfiltered
whose keys
satisfy a predicate. The returned multimap is a live view of
unfiltered
; changes to one affect the other.
The resulting multimap's views have iterators that don't support
remove()
, but all other methods are supported by the multimap and
its views. When adding a key that doesn't satisfy the predicate, the
multimap's put()
, putAll()
, and replaceValues()
methods throw an IllegalArgumentException
.
When methods such as removeAll()
and clear()
are called on
the filtered multimap or its views, only mappings whose keys satisfy the
filter will be removed from the underlying multimap.
The returned multimap isn't threadsafe or serializable, even if
unfiltered
is.
Many of the filtered multimap's methods, such as size()
, iterate
across every key/value mapping in the underlying multimap and determine
which satisfy the filter. When a live view is not needed, it may be
faster to copy the filtered multimap and use the copy.
Warning: keyPredicate
must be consistent with equals,
as documented at Predicate.apply(T)
. Do not provide a predicate such
as Predicates.instanceOf(ArrayList.class)
, which is inconsistent
with equals.
public static <K,V> SetMultimap<K,V> filterKeys(SetMultimap<K,V> unfiltered, Predicate<? super K> keyPredicate)
unfiltered
whose keys
satisfy a predicate. The returned multimap is a live view of
unfiltered
; changes to one affect the other.
The resulting multimap's views have iterators that don't support
remove()
, but all other methods are supported by the multimap and
its views. When adding a key that doesn't satisfy the predicate, the
multimap's put()
, putAll()
, and replaceValues()
methods throw an IllegalArgumentException
.
When methods such as removeAll()
and clear()
are called on
the filtered multimap or its views, only mappings whose keys satisfy the
filter will be removed from the underlying multimap.
The returned multimap isn't threadsafe or serializable, even if
unfiltered
is.
Many of the filtered multimap's methods, such as size()
, iterate
across every key/value mapping in the underlying multimap and determine
which satisfy the filter. When a live view is not needed, it may be
faster to copy the filtered multimap and use the copy.
Warning: keyPredicate
must be consistent with equals,
as documented at Predicate.apply(T)
. Do not provide a predicate such
as Predicates.instanceOf(ArrayList.class)
, which is inconsistent
with equals.
public static <K,V> ListMultimap<K,V> filterKeys(ListMultimap<K,V> unfiltered, Predicate<? super K> keyPredicate)
unfiltered
whose keys
satisfy a predicate. The returned multimap is a live view of
unfiltered
; changes to one affect the other.
The resulting multimap's views have iterators that don't support
remove()
, but all other methods are supported by the multimap and
its views. When adding a key that doesn't satisfy the predicate, the
multimap's put()
, putAll()
, and replaceValues()
methods throw an IllegalArgumentException
.
When methods such as removeAll()
and clear()
are called on
the filtered multimap or its views, only mappings whose keys satisfy the
filter will be removed from the underlying multimap.
The returned multimap isn't threadsafe or serializable, even if
unfiltered
is.
Many of the filtered multimap's methods, such as size()
, iterate
across every key/value mapping in the underlying multimap and determine
which satisfy the filter. When a live view is not needed, it may be
faster to copy the filtered multimap and use the copy.
Warning: keyPredicate
must be consistent with equals,
as documented at Predicate.apply(T)
. Do not provide a predicate such
as Predicates.instanceOf(ArrayList.class)
, which is inconsistent
with equals.
public static <K,V> Multimap<K,V> filterValues(Multimap<K,V> unfiltered, Predicate<? super V> valuePredicate)
unfiltered
whose values
satisfy a predicate. The returned multimap is a live view of
unfiltered
; changes to one affect the other.
The resulting multimap's views have iterators that don't support
remove()
, but all other methods are supported by the multimap and
its views. When adding a value that doesn't satisfy the predicate, the
multimap's put()
, putAll()
, and replaceValues()
methods throw an IllegalArgumentException
.
When methods such as removeAll()
and clear()
are called on
the filtered multimap or its views, only mappings whose value satisfy the
filter will be removed from the underlying multimap.
The returned multimap isn't threadsafe or serializable, even if
unfiltered
is.
Many of the filtered multimap's methods, such as size()
, iterate
across every key/value mapping in the underlying multimap and determine
which satisfy the filter. When a live view is not needed, it may be
faster to copy the filtered multimap and use the copy.
Warning: valuePredicate
must be consistent with
equals, as documented at Predicate.apply(T)
. Do not provide a
predicate such as Predicates.instanceOf(ArrayList.class)
, which is
inconsistent with equals.
public static <K,V> SetMultimap<K,V> filterValues(SetMultimap<K,V> unfiltered, Predicate<? super V> valuePredicate)
unfiltered
whose values
satisfy a predicate. The returned multimap is a live view of
unfiltered
; changes to one affect the other.
The resulting multimap's views have iterators that don't support
remove()
, but all other methods are supported by the multimap and
its views. When adding a value that doesn't satisfy the predicate, the
multimap's put()
, putAll()
, and replaceValues()
methods throw an IllegalArgumentException
.
When methods such as removeAll()
and clear()
are called on
the filtered multimap or its views, only mappings whose value satisfy the
filter will be removed from the underlying multimap.
The returned multimap isn't threadsafe or serializable, even if
unfiltered
is.
Many of the filtered multimap's methods, such as size()
, iterate
across every key/value mapping in the underlying multimap and determine
which satisfy the filter. When a live view is not needed, it may be
faster to copy the filtered multimap and use the copy.
Warning: valuePredicate
must be consistent with
equals, as documented at Predicate.apply(T)
. Do not provide a
predicate such as Predicates.instanceOf(ArrayList.class)
, which is
inconsistent with equals.
public static <K,V> Multimap<K,V> filterEntries(Multimap<K,V> unfiltered, Predicate<? super Map.Entry<K,V>> entryPredicate)
unfiltered
that
satisfy a predicate. The returned multimap is a live view of
unfiltered
; changes to one affect the other.
The resulting multimap's views have iterators that don't support
remove()
, but all other methods are supported by the multimap and
its views. When adding a key/value pair that doesn't satisfy the predicate,
multimap's put()
, putAll()
, and replaceValues()
methods throw an IllegalArgumentException
.
When methods such as removeAll()
and clear()
are called on
the filtered multimap or its views, only mappings whose keys satisfy the
filter will be removed from the underlying multimap.
The returned multimap isn't threadsafe or serializable, even if
unfiltered
is.
Many of the filtered multimap's methods, such as size()
, iterate
across every key/value mapping in the underlying multimap and determine
which satisfy the filter. When a live view is not needed, it may be
faster to copy the filtered multimap and use the copy.
Warning: entryPredicate
must be consistent with
equals, as documented at Predicate.apply(T)
.
public static <K,V> SetMultimap<K,V> filterEntries(SetMultimap<K,V> unfiltered, Predicate<? super Map.Entry<K,V>> entryPredicate)
unfiltered
that
satisfy a predicate. The returned multimap is a live view of
unfiltered
; changes to one affect the other.
The resulting multimap's views have iterators that don't support
remove()
, but all other methods are supported by the multimap and
its views. When adding a key/value pair that doesn't satisfy the predicate,
multimap's put()
, putAll()
, and replaceValues()
methods throw an IllegalArgumentException
.
When methods such as removeAll()
and clear()
are called on
the filtered multimap or its views, only mappings whose keys satisfy the
filter will be removed from the underlying multimap.
The returned multimap isn't threadsafe or serializable, even if
unfiltered
is.
Many of the filtered multimap's methods, such as size()
, iterate
across every key/value mapping in the underlying multimap and determine
which satisfy the filter. When a live view is not needed, it may be
faster to copy the filtered multimap and use the copy.
Warning: entryPredicate
must be consistent with
equals, as documented at Predicate.apply(T)
.
Copyright © 2010-2017. All Rights Reserved.