com.google.common.collect

Class 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 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 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(), 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), keySet(), 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 and Description
      Map<K,Collection<V>> asMap()
      Returns a view of this multimap as a Map from each distinct key to the nonempty collection of that key's associated values.
      void clear()
      Removes all key-value pairs from the multimap, leaving it empty.
      boolean containsEntry(Object key, Object value)
      Returns true if this multimap contains at least one key-value pair with the key key and the value value.
      boolean containsKey(Object key)
      Returns true if this multimap contains at least one key-value pair with the key key.
      boolean containsValue(Object value)
      Returns true if this multimap contains at least one key-value pair with the value value.
      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 view collection of all key-value pairs contained in this multimap, as Map.Entry instances.
      boolean equals(Object object)
      Compares the specified object with this multimap for equality.
      List<V> get(K key)
      Returns a view collection of the values associated with key in this multimap, if any.
      int hashCode()
      Returns the hash code for this multimap.
      boolean isEmpty()
      Returns true if this multimap contains no key-value pairs.
      Multiset<K> keys()
      Returns a view collection containing the key from each key-value pair in this multimap, without collapsing duplicates.
      Set<K> keySet()
      Returns a view collection of all distinct keys contained in this multimap.
      boolean put(K key, V value)
      Stores a key-value pair in the multimap.
      boolean putAll(K key, Iterable<? extends V> values)
      Stores a key-value pair in this multimap for each of values, all using the same key, key.
      boolean putAll(Multimap<? extends K,? extends V> multimap)
      Stores all key-value pairs of multimap in this multimap, in the order returned by multimap.entries().
      boolean remove(Object key, Object value)
      Removes a single key-value pair with the key key and the value value from this multimap, if such exists.
      List<V> removeAll(Object key)
      Removes all values associated with the key 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 this 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 view collection containing the value from each key-value pair contained in this multimap, without collapsing duplicates (so values().size() == size()).

    • 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 this multimap.

        Note: this method does not return the number of distinct keys in the multimap, which is given by keySet().size() or asMap().size(). See the opening section of the Multimap class documentation for clarification.

      • isEmpty

        public boolean isEmpty()
        Description copied from interface: Multimap
        Returns true if this multimap contains no key-value pairs. Equivalent to size() == 0, but can in some cases be more efficient.

      • containsKey

        public boolean containsKey(Object key)
        Description copied from interface: Multimap
        Returns true if this multimap contains at least one key-value pair with the key key.

      • containsValue

        public boolean containsValue(Object value)
        Description copied from interface: Multimap
        Returns true if this multimap contains at least one key-value pair with the value value.

      • put

        public boolean put(K key,
                   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(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>
        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(Object key)
        Removes all values associated with the key 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>
        Returns:
        the values that were removed (possibly empty). The returned 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, leaving it empty.

      • get

        public List<V> get(K key)
        Returns a view collection of the values associated with key in this multimap, if any. Note that when containsKey(key) is false, this 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.

      • values

        public List<V> values()
        Returns a view collection containing the value from each key-value pair contained in this multimap, without collapsing duplicates (so values().size() == size()).

        Changes to the returned collection will update the underlying multimap, and vice versa. However, adding to the returned collection is not possible.

        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.

      • entries

        public List<Map.Entry<K,V>> entries()
        Returns a view collection of all key-value pairs contained in this multimap, as Map.Entry instances.

        Changes to the returned collection or the entries it contains will update the underlying multimap, and vice versa. However, adding to the returned collection is not possible.

        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().

      • containsEntry

        public boolean containsEntry(Object key,
                             Object value)
        Description copied from interface: Multimap
        Returns true if this multimap contains at least one key-value pair with the key key and the value value.

      • remove

        public boolean remove(Object key,
                      Object value)
        Description copied from interface: Multimap
        Removes a single key-value pair with the key key and the value value from this multimap, if such exists. If multiple key-value pairs in the multimap fit this description, which one is removed is unspecified.
        Specified by:
        remove in interface  Multimap<K,V>
        Returns:
        true if the multimap changed

      • putAll

        public boolean putAll(K key,
                      Iterable<? extends V> values)
        Description copied from interface: Multimap
        Stores a key-value pair in this multimap for each of values, all using the same key, key. Equivalent to (but expected to be more efficient than): 
            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>
        Returns:
        true if the multimap changed

      • putAll

        public boolean putAll(Multimap<? extends K,? extends V> multimap)
        Description copied from interface: Multimap
        Stores all key-value pairs of multimap in this multimap, in the order returned by multimap.entries().
        Specified by:
        putAll in interface  Multimap<K,V>
        Returns:
        true if the multimap changed

      • keySet

        public Set<K> keySet()
        Description copied from interface: Multimap
        Returns a view collection of all distinct keys contained in this multimap. Note that the key set contains a key if and only if this multimap maps that key to at least one value.

        Changes to the returned set will update the underlying multimap, and vice versa. However, adding to the returned set is not possible.

      • keys

        public Multiset<K> keys()
        Description copied from interface: Multimap
        Returns a view collection containing the key from each key-value pair in this multimap, without collapsing duplicates. This collection has the same size as this multimap, and keys().count(k) == get(k).size() for all k.

        Changes to the returned multiset will update the underlying multimap, and vice versa. However, adding to the returned collection is not possible.

      • asMap

        public Map<K,Collection<V>> asMap()
        Description copied from interface: Multimap
        Returns a view of this multimap as a Map from each distinct key to the nonempty 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 multimap; 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 multimap, and vice versa. The map does not support put or putAll, nor do its entries support setValue.

      • equals

        public boolean equals(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.

      • 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