Package com.google.common.collect

Class LinkedListMultimap<K,V>

java.lang.Object

com.google.common.collect.LinkedListMultimap<K,V>

All Implemented Interfaces:

ListMultimap<K,V>, Multimap<K,V>, Serializable

@GwtCompatible(serializable=true,
               emulated=true)
public class LinkedListMultimap<K,V>
extends Object
implements ListMultimap<K,V>, Serializable

An implementation of ListMultimap that supports deterministic iteration order for both keys and values. The iteration order is preserved across non-distinct key values. For example, for the following multimap definition:

   

   Multimap<K, V> multimap = LinkedListMultimap.create();
   multimap.put(key1, foo);
   multimap.put(key2, bar);
   multimap.put(key1, baz);

... the iteration order for Multimap.keys() is [key1, key2, key1], and similarly for entries(). Unlike LinkedHashMultimap, the iteration order is kept consistent between keys, entries and values. For example, calling:

   

   map.remove(key1, foo);

changes the entries iteration order to [key2=bar, key1=baz] and the key iteration order to [key2, key1]. The entries() iterator returns mutable map entries, and replaceValues(K, java.lang.Iterable<? extends V>) attempts to preserve iteration order as much as possible.

The collections returned by Multimap.keySet() and asMap iterate through the keys in the order they were first added to the multimap. Similarly, get(K), removeAll(java.lang.Object), and replaceValues(K, java.lang.Iterable<? extends V>) return collections that iterate through the values in the order they were added. The collections generated by entries(), Multimap.keys(), and values() iterate across the key-value mappings in the order they were added to the multimap.

The values() and entries() methods both return a List, instead of the Collection specified by the ListMultimap interface.

The methods get(K), Multimap.keySet(), Multimap.keys(), values(), entries(), and asMap return collections that are views of the multimap. If the multimap is modified while an iteration over any of those collections is in progress, except through the iterator's methods, the results of the iteration are undefined.

Keys and values may be null. All optional multimap methods are supported, and all returned views are modifiable.

This class is not threadsafe when any concurrent operations update the multimap. Concurrent read operations will work correctly. To allow concurrent update operations, wrap your multimap with a call to Multimaps.synchronizedListMultimap(com.google.common.collect.ListMultimap<K, V>).

See the Guava User Guide article on Multimap.

Since:

2.0 (imported from Google Collections Library)

See Also:

Serialized Form

Method Summary

Modifier and Type	Method	Description
Map<K,Collection<V>>	asMap()	Returns a map view that associates each key with the corresponding values in the multimap.
void	clear()	Removes all key-value pairs from the multimap.
boolean	containsEntry(Object key, Object value)	Returns true if the multimap contains the specified key-value pair.
boolean	containsKey(Object key)	Returns true if the multimap contains any values for the specified key.
boolean	containsValue(Object value)	Returns true if the multimap contains the specified value for any key.
static <K,V> LinkedListMultimap<K,V>	create()	Creates a new, empty LinkedListMultimap with the default initial capacity.
static <K,V> LinkedListMultimap<K,V>	create(int expectedKeys)	Constructs an empty LinkedListMultimap with enough capacity to hold the specified number of keys without rehashing.
static <K,V> LinkedListMultimap<K,V>	create(Multimap<? extends K,? extends V> multimap)	Constructs a LinkedListMultimap with the same mappings as the specified Multimap.
List<Map.Entry<K,V>>	entries()	Returns a collection of all key-value pairs.
boolean	equals(Object object)	Compares the specified object with this multimap for equality.
List<V>	get(K key)	Returns a collection view containing the values associated with key in this multimap, if any.
int	hashCode()	Returns the hash code for this multimap.
boolean	isEmpty()	Returns true if the multimap contains no key-value pairs.
Multiset<K>	keys()	Returns a collection, which may contain duplicates, of all keys.
Set<K>	keySet()	Returns the set of all keys, each appearing once in the returned set.
boolean	put(K key, V value)	Stores a key-value pair in the multimap.
boolean	putAll(Multimap<? extends K,? extends V> multimap)	Copies all of another multimap's key-value pairs into this multimap.
boolean	putAll(K key, Iterable<? extends V> values)	Stores key-value pairs in this multimap with one key and multiple values.
boolean	remove(Object key, Object value)	Removes a single key-value pair from the multimap.
List<V>	removeAll(Object key)	Removes all values associated with a given key.
List<V>	replaceValues(K key, Iterable<? extends V> values)	Stores a collection of values with the same key, replacing any existing values for that key.
int	size()	Returns the number of key-value pairs in the multimap.
String	toString()	Returns a string representation of the multimap, generated by calling toString on the map returned by Multimap.asMap().
List<V>	values()	Returns a collection of all values in the multimap.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface com.google.common.collect.ListMultimap

asMap, equals

Methods inherited from interface com.google.common.collect.Multimap

containsEntry, hashCode, keys, keySet, putAll, putAll, remove

Method Detail

create

public static <K,V> LinkedListMultimap<K,V> create()

Creates a new, empty LinkedListMultimap with the default initial capacity.

create

public static <K,V> LinkedListMultimap<K,V> create(int expectedKeys)

Constructs an empty LinkedListMultimap with enough capacity to hold the specified number of keys without rehashing.

Parameters:

expectedKeys - the expected number of distinct keys

Throws:

IllegalArgumentException - if expectedKeys is negative

create

public static <K,V> LinkedListMultimap<K,V> create(Multimap<? extends K,? extends V> multimap)

Constructs a LinkedListMultimap with the same mappings as the specified Multimap. The new multimap has the same Multimap.entries() iteration order as the input multimap.

Parameters:

multimap - the multimap whose contents are copied to this multimap

size

public int size()

Description copied from interface: Multimap

Returns the number of key-value pairs in the multimap.

Specified by:

size in interface Multimap<K,V>

isEmpty

public boolean isEmpty()

Description copied from interface: Multimap

Returns true if the multimap contains no key-value pairs.

Specified by:

isEmpty in interface Multimap<K,V>

containsKey

public boolean containsKey(@Nullable
                           Object key)

Description copied from interface: Multimap

Returns true if the multimap contains any values for the specified key.

Specified by:

containsKey in interface Multimap<K,V>

Parameters:

key - key to search for in multimap

containsValue

public boolean containsValue(@Nullable
                             Object value)

Description copied from interface: Multimap

Returns true if the multimap contains the specified value for any key.

Specified by:

containsValue in interface Multimap<K,V>

Parameters:

value - value to search for in multimap

put

public boolean put(@Nullable
                   K key,
                   @Nullable
                   V value)

Stores a key-value pair in the multimap.

Specified by:

put in interface Multimap<K,V>

Parameters:

key - key to store in the multimap

value - value to store in the multimap

Returns:

true always

replaceValues

public List<V> replaceValues(@Nullable
                             K key,
                             Iterable<? extends V> values)

Stores a collection of values with the same key, replacing any existing values for that key.

If values is empty, this is equivalent to removeAll(key).

If any entries for the specified key already exist in the multimap, their values are changed in-place without affecting the iteration order.

The returned list is immutable and implements RandomAccess.

Specified by:

replaceValues in interface ListMultimap<K,V>

Specified by:

replaceValues in interface Multimap<K,V>

Parameters:

key - key to store in the multimap

values - values to store in the multimap

Returns:

the collection of replaced values, or an empty collection if no values were previously associated with the key. The collection may be modifiable, but updating it will have no effect on the multimap.

removeAll

public List<V> removeAll(@Nullable
                         Object key)

Removes all values associated with a given key.

Once this method returns, key will not be mapped to any values, so it will not appear in Multimap.keySet(), Multimap.asMap(), or any other views.

Because the values for a given key may have duplicates and follow the insertion ordering, this method returns a List, instead of the Collection specified in the Multimap interface.

The returned list is immutable and implements RandomAccess.

Specified by:

removeAll in interface ListMultimap<K,V>

Specified by:

removeAll in interface Multimap<K,V>

Parameters:

key - key of entries to remove from the multimap

Returns:

the collection of removed values, or an empty collection if no values were associated with the provided key. The collection may be modifiable, but updating it will have no effect on the multimap.

clear

public void clear()

Description copied from interface: Multimap

Removes all key-value pairs from the multimap.

Specified by:

clear in interface Multimap<K,V>

get

public List<V> get(@Nullable
                   K key)

Returns a collection view containing the values associated with key in this multimap, if any. Note that even when (containsKey(key) is false, get(key) still returns an empty collection, not null.

Changes to the returned collection will update the underlying multimap, and vice versa.

Because the values for a given key may have duplicates and follow the insertion ordering, this method returns a List, instead of the Collection specified in the Multimap interface.

If the multimap is modified while an iteration over the list is in progress (except through the iterator's own add, set or remove operations) the results of the iteration are undefined.

The returned list is not serializable and does not have random access.

Specified by:

get in interface ListMultimap<K,V>

Specified by:

get in interface Multimap<K,V>

Parameters:

key - key to search for in multimap

Returns:

a view collection containing the zero or more values that the key maps to

values

public List<V> values()

Returns a collection of all values in the multimap. Changes to the returned collection will update the underlying multimap, and vice versa.

The iterator generated by the returned collection traverses the values in the order they were added to the multimap. Because the values may have duplicates and follow the insertion ordering, this method returns a List, instead of the Collection specified in the ListMultimap interface.

Specified by:

values in interface Multimap<K,V>

Returns:

collection of values, which may include the same value multiple times if it occurs in multiple mappings

entries

public List<Map.Entry<K,V>> entries()

Returns a collection of all key-value pairs. Changes to the returned collection will update the underlying multimap, and vice versa. The entries collection does not support the add or addAll operations.

The iterator generated by the returned collection traverses the entries in the order they were added to the multimap. Because the entries may have duplicates and follow the insertion ordering, this method returns a List, instead of the Collection specified in the ListMultimap interface.

An entry's Map.Entry.getKey() method always returns the same key, regardless of what happens subsequently. As long as the corresponding key-value mapping is not removed from the multimap, Map.Entry.getValue() returns the value from the multimap, which may change over time, and Map.Entry.setValue(V) modifies that value. Removing the mapping from the multimap does not alter the value returned by getValue(), though a subsequent setValue() call won't update the multimap but will lead to a revised value being returned by getValue().

Specified by:

entries in interface Multimap<K,V>

Returns:

collection of map entries consisting of key-value pairs

containsEntry

public boolean containsEntry(@Nullable
                             Object key,
                             @Nullable
                             Object value)

Description copied from interface: Multimap

Returns true if the multimap contains the specified key-value pair.

Specified by:

containsEntry in interface Multimap<K,V>

Parameters:

key - key to search for in multimap

value - value to search for in multimap

remove

public boolean remove(@Nullable
                      Object key,
                      @Nullable
                      Object value)

Description copied from interface: Multimap

Removes a single key-value pair from the multimap.

Specified by:

remove in interface Multimap<K,V>

Parameters:

key - key of entry to remove from the multimap

value - value of entry to remove the multimap

Returns:

true if the multimap changed

putAll

public boolean putAll(@Nullable
                      K key,
                      Iterable<? extends V> values)

Description copied from interface: Multimap

Stores key-value pairs in this multimap with one key and multiple values.

This is equivalent to

   
 
   for (V value : values) {
     put(key, value);
   } 

In particular, this is a no-op if values is empty.

Specified by:

putAll in interface Multimap<K,V>

Parameters:

key - key to store in the multimap

values - values to store in the multimap

Returns:

true if the multimap changed

putAll

public boolean putAll(Multimap<? extends K,? extends V> multimap)

Description copied from interface: Multimap

Copies all of another multimap's key-value pairs into this multimap. The order in which the mappings are added is determined by multimap.entries().

Specified by:

putAll in interface Multimap<K,V>

Parameters:

multimap - mappings to store in this multimap

Returns:

true if the multimap changed

keySet

public Set<K> keySet()

Description copied from interface: Multimap

Returns the set of all keys, each appearing once in the returned set. Changes to the returned set will update the underlying multimap, and vice versa.

Note that the key set contains a key if and only if this multimap maps that key to at least one value.

Specified by:

keySet in interface Multimap<K,V>

Returns:

the collection of distinct keys

keys

public Multiset<K> keys()

Description copied from interface: Multimap

Returns a collection, which may contain duplicates, of all keys. The number of times of key appears in the returned multiset equals the number of mappings the key has in the multimap. Changes to the returned multiset will update the underlying multimap, and vice versa.

Specified by:

keys in interface Multimap<K,V>

Returns:

a multiset with keys corresponding to the distinct keys of the multimap and frequencies corresponding to the number of values that each key maps to

asMap

public Map<K,Collection<V>> asMap()

Description copied from interface: Multimap

Returns a map view that associates each key with the corresponding values in the multimap. Changes to the returned map, such as element removal, will update the underlying multimap. The map does not support setValue() on its entries, put, or putAll.

When passed a key that is present in the map, asMap().get(Object) has the same behavior as Multimap.get(K), returning a live collection. When passed a key that is not present, however, asMap().get(Object) returns null instead of an empty collection.

Specified by:

asMap in interface Multimap<K,V>

Returns:

a map view from a key to its collection of values

equals

public boolean equals(@Nullable
                      Object object)

Description copied from interface: Multimap

Compares the specified object with this multimap for equality. Two multimaps are equal when their map views, as returned by Multimap.asMap(), are also equal.

In general, two multimaps with identical key-value mappings may or may not be equal, depending on the implementation. For example, two SetMultimap instances with the same key-value mappings are equal, but equality of two ListMultimap instances depends on the ordering of the values for each key.

A non-empty SetMultimap cannot be equal to a non-empty ListMultimap, since their Multimap.asMap() views contain unequal collections as values. However, any two empty multimaps are equal, because they both have empty Multimap.asMap() views.

Specified by:

equals in interface Multimap<K,V>

Overrides:

equals in class Object

hashCode

public int hashCode()

Returns the hash code for this multimap.

The hash code of a multimap is defined as the hash code of the map view, as returned by Multimap.asMap().

Specified by:

hashCode in interface Multimap<K,V>

Overrides:

hashCode in class Object

See Also:

Map.hashCode()

toString

public String toString()

Returns a string representation of the multimap, generated by calling toString on the map returned by Multimap.asMap().

Overrides:

toString in class Object

Returns:

a string representation of the multimap