Package com.google.common.collect

Class ForwardingMultimap<K,​V>

  • All Implemented Interfaces:
    Multimap<K,​V>
    Direct Known Subclasses:
    ForwardingListMultimap, ForwardingSetMultimap
    @GwtCompatible
public abstract class ForwardingMultimap<K,​V>
extends ForwardingObject
implements Multimap<K,​V>
    A multimap which forwards all its method calls to another multimap. Subclasses should override one or more methods to modify the behavior of the backing multimap as desired per the decorator pattern.

    default method warning: This class does not forward calls to default methods. Instead, it inherits their default implementations. When those implementations invoke methods, they invoke methods on the ForwardingMultimap.

    Since:
    2.0
    Author:
    Robert Konigsberg

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      protected ForwardingMultimap()
      Constructor for use by subclasses.

    • Method Summary

      All Methods Instance Methods Abstract 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​(@Nullable Object key, @Nullable Object value)
      Returns true if this multimap contains at least one key-value pair with the key key and the value value.
      boolean containsKey​(@Nullable Object key)
      Returns true if this multimap contains at least one key-value pair with the key key.
      boolean containsValue​(@Nullable Object value)
      Returns true if this multimap contains at least one key-value pair with the value value.
      protected abstract Multimap<K,​V> delegate()
      Returns the backing delegate instance that methods are forwarded to.
      Collection<Map.Entry<K,​V>> entries()
      Returns a view collection of all key-value pairs contained in this multimap, as Map.Entry instances.
      boolean equals​(@Nullable Object object)
      Indicates whether some other object is "equal to" this one.
      Collection<V> get​(@Nullable K key)
      Returns a view collection of the values associated with key in this multimap, if any.
      int hashCode()
      Returns a hash code value for the object.
      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 this 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​(@Nullable Object key, @Nullable Object value)
      Removes a single key-value pair with the key key and the value value from this multimap, if such exists.
      Collection<V> removeAll​(@Nullable Object key)
      Removes all values associated with the key key.
      Collection<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.
      Collection<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()).

    • Constructor Detail

    • Method Detail

      • delegate

        protected abstract Multimap<K,​V> delegate()
        Description copied from class: ForwardingObject
        Returns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such as ForwardingSet.delegate(). Concrete subclasses override this method to supply the instance being decorated.
        Specified by:
        delegate in class ForwardingObject

      • 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.

        Specified by:
        asMap in interface Multimap<K,​V>

      • clear

        public void clear()
        Description copied from interface: Multimap
        Removes all key-value pairs from the multimap, leaving it empty.
        Specified by:
        clear in interface Multimap<K,​V>

      • entries

        public Collection<Map.Entry<K,​V>> entries()
        Description copied from interface: Multimap
        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.

        Specified by:
        entries in interface Multimap<K,​V>

      • get

        public Collection<V> get​(@Nullable K key)
        Description copied from interface: Multimap
        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.

        Specified by:
        get in interface Multimap<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,​V>

      • 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,​V>

      • 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.

        Specified by:
        keySet in interface Multimap<K,​V>

      • put

        @CanIgnoreReturnValue
public boolean put​(K key,
                   V value)
        Description copied from interface: Multimap
        Stores a key-value pair in this multimap.

        Some multimap implementations allow duplicate key-value pairs, in which case put always adds a new key-value pair and increases the multimap size by 1. Other implementations prohibit duplicates, and storing a key-value pair that's already in the multimap has no effect.

        Specified by:
        put in interface Multimap<K,​V>
        Returns:
        true if the method increased the size of the multimap, or false if the multimap already contained the key-value pair and doesn't allow duplicates

      • 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,​V>
        Returns:
        true if the multimap changed

      • putAll

        @CanIgnoreReturnValue
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

      • remove

        @CanIgnoreReturnValue
public boolean remove​(@Nullable Object key,
                      @Nullable 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

      • replaceValues

        @CanIgnoreReturnValue
public Collection<V> replaceValues​(K key,
                                   Iterable<? extends V> values)
        Description copied from interface: Multimap
        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).

        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.

      • 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,​V>

      • values

        public Collection<V> values()
        Description copied from interface: Multimap
        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.

        Specified by:
        values in interface Multimap<K,​V>

      • equals

        public boolean equals​(@Nullable Object object)
        Description copied from class: java.lang.Object
        Indicates whether some other object is "equal to" this one.

        The equals method implements an equivalence relation on non-null object references:

        • It is reflexive: for any non-null reference value x, x.equals(x) should return true.
        • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
        • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
        • It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
        • For any non-null reference value x, x.equals(null) should return false.

        The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

        Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

        Specified by:
        equals in interface Multimap<K,​V>
        Overrides:
        equals in class Object
        Parameters:
        object - the reference object with which to compare.
        Returns:
        true if this object is the same as the obj argument; false otherwise.
        See Also:
        Object.hashCode(), HashMap

      • hashCode

        public int hashCode()
        Description copied from class: java.lang.Object
        Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

        The general contract of hashCode is:

        • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
        • If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
        • It is not required that if two objects are unequal according to the Object.equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

        As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (The hashCode may or may not be implemented as some function of an object's memory address at some point in time.)

        Specified by:
        hashCode in interface Multimap<K,​V>
        Overrides:
        hashCode in class Object
        Returns:
        a hash code value for this object.
        See Also:
        Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)