Package com.google.common.collect

Class LinkedHashMultimap<K extends @Nullable Object,​V extends @Nullable Object>

  • All Implemented Interfaces:
    Multimap<K,​V>, SetMultimap<K,​V>, Serializable
    @GwtCompatible(serializable=true,
               emulated=true)
public final class LinkedHashMultimap<K extends @Nullable Object,​V extends @Nullable Object>
extends Object
    Implementation of Multimap that does not allow duplicate key-value entries and that returns collections whose iterators follow the ordering in which the data was added to the multimap.

    The collections returned by keySet, keys, and asMap iterate through the keys in the order they were first added to the multimap. Similarly, get, removeAll, and replaceValues return collections that iterate through the values in the order they were added. The collections generated by entries and values iterate across the key-value mappings in the order they were added to the multimap.

    The iteration ordering of the collections generated by keySet, keys, and asMap has a few subtleties. As long as the set of keys remains unchanged, adding or removing mappings does not affect the key iteration order. However, if you remove all values associated with a key and then add the key back to the multimap, that key will come last in the key iteration order.

    The multimap does not store duplicate key-value pairs. Adding a new key-value pair equal to an existing key-value pair has no effect.

    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.synchronizedSetMultimap(com.google.common.collect.SetMultimap<K, V>).

    Warning: Do not modify either a key or a value of a LinkedHashMultimap in a way that affects its Object.equals(java.lang.Object) behavior. Undefined behavior and bugs will result.

    See the Guava User Guide article on Multimap.

    Since:
    2.0
    Author:
    Jared Levy, Louis Wasserman
    See Also:
    Serialized Form

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method 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 extends @Nullable Object,​V extends @Nullable Object>
      LinkedHashMultimap<K,​V>      		 create()
      Creates a new, empty LinkedHashMultimap with the default initial capacities.
      static <K extends @Nullable Object,​V extends @Nullable Object>
      LinkedHashMultimap<K,​V>      		 create​(int expectedKeys, int expectedValuesPerKey)
      Constructs an empty LinkedHashMultimap with enough capacity to hold the specified numbers of keys and values without rehashing.
      static <K extends @Nullable Object,​V extends @Nullable Object>
      LinkedHashMultimap<K,​V>      		 create​(Multimap<? extends K,​? extends V> multimap)
      Constructs a LinkedHashMultimap with the same mappings as the specified multimap.
      Set<Map.Entry<K,​V>> entries()
      Returns a set of all key-value pairs.
      boolean equals​(Object object)
      Compares the specified object to this multimap for equality.
      Set<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​(Multimap<? extends K,​? extends V> multimap)
      Stores all key-value pairs of multimap in this multimap, in the order returned by multimap.entries().
      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 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.
      Set<V> removeAll​(Object key)
      Removes all values associated with the key key.
      Set<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().
      Collection<V> values()
      Returns a collection of all values in the multimap.

    • Method Detail

      • create

        public static <K extends @Nullable Object,​V extends @Nullable Object> LinkedHashMultimap<K,​V> create​(int expectedKeys,
                                                                                                                 int expectedValuesPerKey)
        Constructs an empty LinkedHashMultimap with enough capacity to hold the specified numbers of keys and values without rehashing.
        Parameters:
        expectedKeys - the expected number of distinct keys
        expectedValuesPerKey - the expected average number of values per key
        Throws:
        IllegalArgumentException - if expectedKeys or expectedValuesPerKey is negative

      • create

        public static <K extends @Nullable Object,​V extends @Nullable Object> LinkedHashMultimap<K,​V> create​(Multimap<? extends K,​? extends V> multimap)
        Constructs a LinkedHashMultimap with the same mappings as the specified multimap. If a key-value mapping appears multiple times in the input multimap, it only appears once in the constructed multimap. The new multimap has the same Multimap.entries() iteration order as the input multimap, except for excluding duplicate mappings.
        Parameters:
        multimap - the multimap whose contents are copied to this multimap

      • replaceValues

        @CanIgnoreReturnValue
public Set<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).

        The returned collection is immutable.

        Because a SetMultimap has unique values for a given key, this method returns a Set, instead of the Collection specified in the Multimap interface.

        Any duplicates in values will be stored in the multimap once.

        If values is not empty and the multimap already contains a mapping for key, the keySet() ordering is unchanged. However, the provided values always come last in the entries() and values() iteration orderings.

        Specified by:
        replaceValues in interface Multimap<K extends @Nullable Object,​V extends @Nullable Object>
        Specified by:
        replaceValues in interface SetMultimap<K extends @Nullable Object,​V extends @Nullable Object>
        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.

      • entries

        public Set<Map.Entry<K,​V>> entries()
        Returns a set of all key-value pairs. Changes to the returned set will update the underlying multimap, and vice versa. The entries set does not support the add or addAll operations.

        The iterator generated by the returned set traverses the entries in the order they were added to the multimap.

        Each entry is an immutable snapshot of a key-value mapping in the multimap, taken at the time the entry is returned by a method call to the collection or its iterator.

        Specified by:
        entries in interface Multimap<K extends @Nullable Object,​V extends @Nullable Object>
        Specified by:
        entries in interface SetMultimap<K extends @Nullable Object,​V extends @Nullable Object>

      • keySet

        public Set<K> keySet()
        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.

        The iterator generated by the returned set traverses the keys in the order they were first added to the multimap.

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

        Specified by:
        keySet in interface Multimap<K extends @Nullable Object,​V extends @Nullable Object>

      • values

        public Collection<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.

        Specified by:
        values in interface Multimap<K extends @Nullable Object,​V extends @Nullable Object>

      • get

        public Set<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.

        The returned collection is not serializable.

        Because a SetMultimap has unique values for a given key, this method returns a Set, instead of the Collection specified in the Multimap interface.

        Specified by:
        get in interface Multimap<K extends @Nullable Object,​V extends @Nullable Object>
        Specified by:
        get in interface SetMultimap<K extends @Nullable Object,​V extends @Nullable Object>

      • asMap

        public 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. 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.

        Though the method signature doesn't say so explicitly, the returned map has Set values.

        Specified by:
        asMap in interface Multimap<K extends @Nullable Object,​V extends @Nullable Object>
        Specified by:
        asMap in interface SetMultimap<K extends @Nullable Object,​V extends @Nullable Object>

      • put

        @CanIgnoreReturnValue
public boolean put​(K key,
                   V value)
        Stores a key-value pair in the multimap.
        Specified by:
        put in interface Multimap<K extends @Nullable Object,​V extends @Nullable Object>
        Parameters:
        key - key to store in the multimap
        value - value to store in the multimap
        Returns:
        true if the method increased the size of the multimap, or false if the multimap already contained the key-value pair

      • 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.

        Specified by:
        size in interface Multimap<K extends @Nullable Object,​V extends @Nullable Object>

      • 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.
        Specified by:
        isEmpty in interface Multimap<K extends @Nullable Object,​V extends @Nullable Object>

      • putAll

        @CanIgnoreReturnValue
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 extends @Nullable Object,​V extends @Nullable Object>
        Returns:
        true if the multimap changed

      • 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.

        Specified by:
        keys in interface Multimap<K extends @Nullable Object,​V extends @Nullable Object>

      • 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