Interface MultiMap<K,V>

Type Parameters:
K - the key type
V - the value type
All Known Implementing Classes:
IdMultiHashMap, MultiHashMap, SynchronizedMultiMap, TypeMultiHashMap, UnmodifiableMultiMap
public interface MultiMap<K,V>
A map that associates each key with a collection of values rather than a single value. Putting several values under one key keeps all of them; get(K) returns the whole collection for a key (an empty collection if the key is absent), and size() counts key/value pairs, not keys. Keys and values are never null; the mutators reject null arguments. The collections returned by get(K), keySet(), values(), and asMap() are unmodifiable views. An implementation reports whether it accepts changes through isModifiable(); a read-only implementation throws UnsupportedException from its mutators. Whether duplicate values are kept under a key is implementation-defined. See MultiHashMap for the standard implementation and Collections for read-only and synchronized wrappers.

  • Method Summary

    Modifier and Type
    Method
    Description
    Map<K, Collection<V>>
    asMap()
    Gets a Map of this MultiMap.
    void
    clear()
    Removes all of the mappings from this map.
    boolean
    containsKey(K key)
    Tests if this map contains a mapping for the specified key.
    boolean
    containsKeyValue(K key, V value)
    Tests the map contains the key and value specified.
    boolean
    containsValue(V value)
    Tests the map contains the value specified.
    Collection<V>
    get(K key)
    Gets the values to which the specified key is mapped.
    boolean
    isEmpty()
    Tests if this map contains no key-value mappings.
    boolean
    isModifiable()
    Tests if this map can be modified.
    Collection<K>
    keySet()
    Returns an immutable Collection view of the keys contained in this map.
    void
    put(K key, V value)
    Associates the specified value with the specified key in this map.
    void
    putAll(Map<K, Collection<? extends V>> map)
    Stores a map of keys and values inside this map.
    void
    putAll(K key, Collection<? extends V> values)
    Adds a collection of values to to a key in this map
    void
    putAll(MultiMap<K, ? extends V> map)
    Stores a Multimap inside this map.
    void
    remove(K key)
    Removes the mapping for a key and all its related values.
    void
    remove(K key, V value)
    Removes a specific key/value pair from the map.
    void
    removeValue(V value)
    Removes a value.
    long
    size()
    Returns the number of key-value mappings in this map.
    Collection<V>
    values()
    Returns a Collection view of the values contained in this map.

  • Method Details

    • isModifiable

      boolean isModifiable()
      Tests if this map can be modified.
      Returns:
      true if the map can be modified, false if read-only

    • size

      long size()
      Returns the number of key-value mappings in this map.
      Returns:
      the number of key-value mappings in this map

    • isEmpty

      boolean isEmpty()
      Tests if this map contains no key-value mappings.
      Returns:
      true if this map contains no key-value mappings, false otherwise

    • containsKey

      boolean containsKey(K key)
      Tests if this map contains a mapping for the specified key.
      Parameters:
      key - the key whose presence in this map is to be tested
      Returns:
      true if this map contains a mapping for the specified key, false otherwise
      Throws:
      NullArgumentException - key is null

    • containsValue

      boolean containsValue(V value)
      Tests the map contains the value specified.
      Parameters:
      value - the value to search for
      Returns:
      true if the map contains the value, false otherwise
      Throws:
      NullArgumentException - value is null

    • containsKeyValue

      boolean containsKeyValue(K key, V value)
      Tests the map contains the key and value specified.
      Parameters:
      key - the key
      value - the value
      Returns:
      true if the map contains the key/value pair, false otherwise
      Throws:
      NullArgumentException - key or value is null

    • get

      Collection<V> get(K key)
      Gets the values to which the specified key is mapped. If the key is not defined, this method returns an empty list.
      Parameters:
      key - the key
      Returns:
      a collection of the values for the given key or an empty collection if the key is not found
      Throws:
      NullArgumentException - key is null

    • put

      void put(K key, V value)
      Associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced.
      Parameters:
      key - key with which the specified value is to be associated
      value - value to be associated with the specified key
      Throws:
      NullArgumentException - key or value is null
      UnsupportedException - map is not modifiable

    • putAll

      void putAll(K key, Collection<? extends V> values)
      Adds a collection of values to to a key in this map
      Parameters:
      key - the key
      values - the values
      Throws:
      NullArgumentException - key or values is null
      UnsupportedException - map is not modifiable

    • putAll

      void putAll(Map<K, Collection<? extends V>> map)
      Stores a map of keys and values inside this map.
      Parameters:
      map - the map to store
      Throws:
      NullArgumentException - map is null
      UnsupportedException - map is not modifiable

    • putAll

      void putAll(MultiMap<K, ? extends V> map)
      Stores a Multimap inside this map.
      Parameters:
      map - the map to store
      Throws:
      NullArgumentException - map is null
      UnsupportedException - map is not modifiable

    • remove

      void remove(K key)
      Removes the mapping for a key and all its related values.
      Parameters:
      key - whose mapping is to be removed from the map
      Throws:
      NullArgumentException - key is null
      UnsupportedException - map is not modifiable

    • remove

      void remove(K key, V value)
      Removes a specific key/value pair from the map. The item is removed from the collection mapped to the specified key. Other values attached to that key are unaffected.
      Parameters:
      key - the key
      value - the value to remove
      Throws:
      NullArgumentException - key or value is null
      UnsupportedException - map is not modifiable

    • removeValue

      void removeValue(V value)
      Removes a value.
      Parameters:
      value - to be removed from the map
      Throws:
      NullArgumentException - value is null

    • clear

      void clear()
      Removes all of the mappings from this map. The map will be empty after this call returns.
      Throws:
      UnsupportedException - map is not modifiable

    • keySet

      Collection<K> keySet()
      Returns an immutable Collection view of the keys contained in this map.
      Returns:
      a set view of the keys contained in this map

    • values

      Collection<V> values()
      Returns a Collection view of the values contained in this map.
      Returns:
      a collection of the values

    • asMap

      Map<K, Collection<V>> asMap()
      Gets a Map of this MultiMap.
      Returns:
      a map view of this MultiMap