Package com.google.common.collect

Class ImmutableSetMultimap<K,​V>

    • Method Detail

      • toImmutableSetMultimap

        public static <T extends @Nullable Object,​K,​V> Collector<T,​?,​ImmutableSetMultimap<K,​V>> toImmutableSetMultimap​(Function<? super T,​? extends K> keyFunction,
                                                                                                                                             Function<? super T,​? extends V> valueFunction)
        Returns a Collector that accumulates elements into an ImmutableSetMultimap whose keys and values are the result of applying the provided mapping functions to the input elements.

        For streams with defined encounter order (as defined in the Ordering section of the java.util.stream Javadoc), that order is preserved, but entries are grouped by key.

        Example: 

        
 static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
         .collect(toImmutableSetMultimap(str -> str.charAt(0), str -> str.substring(1)));

 // is equivalent to

 static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
     new ImmutableSetMultimap.Builder<Character, String>()
         .put('b', "anana")
         .putAll('a', "pple", "sparagus")
         .putAll('c', "arrot", "herry")
         .build();
        Since:
        21.0

      • flatteningToImmutableSetMultimap

        public static <T extends @Nullable Object,​K,​V> Collector<T,​?,​ImmutableSetMultimap<K,​V>> flatteningToImmutableSetMultimap​(Function<? super T,​? extends K> keyFunction,
                                                                                                                                                       Function<? super T,​? extends Stream<? extends V>> valuesFunction)
        Returns a Collector accumulating entries into an ImmutableSetMultimap. 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 ImmutableSetMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
         .collect(
             flatteningToImmutableSetMultimap(
                  str -> str.charAt(0),
                  str -> str.substring(1).chars().mapToObj(c -> (char) c));

 // is equivalent to

 static final ImmutableSetMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
     ImmutableSetMultimap.<Character, Character>builder()
         .putAll('b', Arrays.asList('a', 'n', 'a', 'n', 'a'))
         .putAll('a', Arrays.asList('p', 'p', 'l', 'e'))
         .putAll('c', Arrays.asList('a', 'r', 'r', 'o', 't'))
         .putAll('a', Arrays.asList('s', 'p', 'a', 'r', 'a', 'g', 'u', 's'))
         .putAll('c', Arrays.asList('h', 'e', 'r', 'r', 'y'))
         .build();

 // after deduplication, the resulting multimap is equivalent to

 static final ImmutableSetMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
     ImmutableSetMultimap.<Character, Character>builder()
         .putAll('b', Arrays.asList('a', 'n'))
         .putAll('a', Arrays.asList('p', 'l', 'e', 's', 'a', 'r', 'g', 'u'))
         .putAll('c', Arrays.asList('a', 'r', 'o', 't', 'h', 'e', 'y'))
         .build();
 
 }
        Since:
        21.0

      • of

        public static <K,​V> ImmutableSetMultimap<K,​V> of()
        Returns the empty multimap.

        Performance note: the instance returned is a singleton.

      • of

        public static <K,​V> ImmutableSetMultimap<K,​V> of​(K k1,
                                                             V v1)
        Returns an immutable multimap containing a single entry.

      • of

        public static <K,​V> ImmutableSetMultimap<K,​V> of​(K k1,
                                                             V v1,
                                                             K k2,
                                                             V v2)
        Returns an immutable multimap containing the given entries, in order. Repeated occurrences of an entry (according to Object.equals(java.lang.Object)) after the first are ignored.

      • of

        public static <K,​V> ImmutableSetMultimap<K,​V> of​(K k1,
                                                             V v1,
                                                             K k2,
                                                             V v2,
                                                             K k3,
                                                             V v3)
        Returns an immutable multimap containing the given entries, in order. Repeated occurrences of an entry (according to Object.equals(java.lang.Object)) after the first are ignored.

      • of

        public static <K,​V> ImmutableSetMultimap<K,​V> of​(K k1,
                                                             V v1,
                                                             K k2,
                                                             V v2,
                                                             K k3,
                                                             V v3,
                                                             K k4,
                                                             V v4)
        Returns an immutable multimap containing the given entries, in order. Repeated occurrences of an entry (according to Object.equals(java.lang.Object)) after the first are ignored.

      • of

        public static <K,​V> ImmutableSetMultimap<K,​V> of​(K k1,
                                                             V v1,
                                                             K k2,
                                                             V v2,
                                                             K k3,
                                                             V v3,
                                                             K k4,
                                                             V v4,
                                                             K k5,
                                                             V v5)
        Returns an immutable multimap containing the given entries, in order. Repeated occurrences of an entry (according to Object.equals(java.lang.Object)) after the first are ignored.

      • builderWithExpectedKeys

        public static <K,​V> ImmutableSetMultimap.Builder<K,​V> builderWithExpectedKeys​(int expectedKeys)
        Returns a new builder with a hint for how many distinct keys are expected to be added. The generated builder is equivalent to that returned by builder(), but may perform better if expectedKeys is a good estimate.
        Throws:
        IllegalArgumentException - if expectedKeys is negative
        Since:
        33.3.0

      • copyOf

        public static <K,​V> ImmutableSetMultimap<K,​V> copyOf​(Multimap<? extends K,​? extends V> multimap)
        Returns an immutable set multimap containing the same mappings as multimap. The generated multimap's key and value orderings correspond to the iteration ordering of the multimap.asMap() view. Repeated occurrences of an entry in the multimap after the first are ignored.

        Despite the method name, this method attempts to avoid actually copying the data when it is safe to do so. The exact circumstances under which a copy will or will not be performed are undocumented and subject to change.

        Throws:
        NullPointerException - if any key or value in multimap is null

      • copyOf

        public static <K,​V> ImmutableSetMultimap<K,​V> copyOf​(Iterable<? extends Map.Entry<? extends K,​? extends V>> entries)
        Returns an immutable multimap containing the specified entries. The returned multimap iterates over keys in the order they were first encountered in the input, and the values for each key are iterated in the order they were encountered. If two values for the same key are equal, the first value encountered is used.
        Throws:
        NullPointerException - if any key, value, or entry is null
        Since:
        19.0

      • get

        public ImmutableSet<V> get​(K key)
        Returns an immutable set of the values for the given key. If no mappings in the multimap have the provided key, an empty immutable set is returned. The values are in the same order as the parameters used to build this multimap.
        Specified by:
        get in interface Multimap<K,​V>
        Specified by:
        get in interface SetMultimap<K,​V>
        Specified by:
        get in class ImmutableMultimap<K,​V>

      • inverse

        public ImmutableSetMultimap<V,​K> inverse()
        Returns an immutable multimap which is the inverse of this one. For every key-value mapping in the original, the result will have a mapping with key and value reversed.

        Because an inverse of a set multimap cannot contain multiple pairs with the same key and value, this method returns an ImmutableSetMultimap rather than the ImmutableMultimap specified in the ImmutableMultimap class.

        Specified by:
        inverse in class ImmutableMultimap<K,​V>

      • 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>

      • equals

        public boolean equals​(@CheckForNull
                      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 extends @Nullable Object,​V extends @Nullable Object>
        Overrides:
        equals in class 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