org.apache.commons.collections4

Interface SetValuedMap<K,V>

  • All Superinterfaces:
    MultiValuedMap<K,V>
    All Known Implementing Classes:
    AbstractSetValuedMap, HashSetValuedHashMap 

    public interface SetValuedMap<K,V>
extends MultiValuedMap<K,V>
    Defines a map that holds a set of values against each key.

    A SetValuedMap is a Map with slightly different semantics:

    • Putting a value into the map will add the value to a Set at that key.
    • Getting a value will return a Set, holding all the values put to that key.
    Since:
    4.1

    • Method Detail

      • get

        Set<V> get(K key)
        Gets the set of values associated with the specified key.

        Implementations typically return an empty Set if no values have been mapped to the key.

        Specified by:
        get in interface  MultiValuedMap<K,V>
        Parameters:
        key - the key to retrieve
        Returns:
        the Set of values, implementations should return an empty Set for no mapping
        Throws:
        NullPointerException - if the key is null and null keys are invalid

      • remove

        Set<V> remove(Object key)
        Removes all values associated with the specified key.

        The returned set may be modifiable, but updates will not be propagated to this set-valued map. In case no mapping was stored for the specified key, an empty, unmodifiable set will be returned.

        Specified by:
        remove in interface  MultiValuedMap<K,V>
        Parameters:
        key - the key to remove values from
        Returns:
        the Set of values removed, implementations should return null for no mapping found, but may return an empty collection
        Throws:
        UnsupportedOperationException - if the map is unmodifiable
        NullPointerException - if the key is null and null keys are invalid