Package org.apache.commons.collections4

Interface ListValuedMap<K,V>

Type Parameters:

K - the type of the keys in this map

V - the type of the values in this map

All Superinterfaces:

MultiValuedMap<K,V>

All Known Implementing Classes:

AbstractListValuedMap, ArrayListValuedHashMap

public interface ListValuedMap<K,V>
extends MultiValuedMap<K,V>

Defines a map that holds a list of values against each key.

A ListValuedMap is a Map with slightly different semantics:

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

Since:

4.1

Method Summary

Modifier and Type	Method	Description
java.util.List<V>	get(K key)	Gets the list of values associated with the specified key.
java.util.List<V>	remove(java.lang.Object key)	Removes all values associated with the specified key.

Methods inherited from interface org.apache.commons.collections4.MultiValuedMap

asMap, clear, containsKey, containsMapping, containsValue, entries, isEmpty, keys, keySet, mapIterator, put, putAll, putAll, putAll, removeMapping, size, values

Method Detail

get

java.util.List<V> get(K key)

Gets the list of values associated with the specified key.

This method will return an empty list if MultiValuedMap.containsKey(Object) returns false. Changes to the returned list will update the underlying ListValuedMap and vice-versa.

Specified by:

get in interface MultiValuedMap<K,V>

Parameters:

key - the key to retrieve

Returns:

the List of values, implementations should return an empty List for no mapping

Throws:

java.lang.NullPointerException - if the key is null and null keys are invalid

remove

java.util.List<V> remove(java.lang.Object key)

Removes all values associated with the specified key.

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

Specified by:

remove in interface MultiValuedMap<K,V>

Parameters:

key - the key to remove values from

Returns:

the List of values removed, implementations typically return an empty, unmodifiable List for no mapping found

Throws:

java.lang.UnsupportedOperationException - if the map is unmodifiable

java.lang.NullPointerException - if the key is null and null keys are invalid