No standard wrapper implementation for MultiValuedMap

Question

Am I missing something, or is there really no default implementation of Apache's new MultiValuedMap that could be used to simply wrap provided Map<K, ? extends Collection<V>>?

In other words, I am looking for a direct replacement of the now deprecated MapUtils.multiValueMap factory method: none of existing implementations like HashSetValuedHashMap meet my needs as I need to use IdentifyHashMap as backend map

score 0 · Accepted Answer · answered Feb 04 '20 at 10:04

In the end I had to implement necessary helper method myself:

public static <K, V, C extends Collection<V>> MultiValuedMap<K, V> multiValueMap(Map<K, C> map,
        final Factory<C> collectionFactory) {
    return new AbstractMultiValuedMap<K, V>(map) {
        @Override
        protected Collection<V> createCollection() {
            return collectionFactory.create();
        }
    };
}

Though, with how trivial the implementation is, I cannot believe it is not there in commons-collections already.

No standard wrapper implementation for MultiValuedMap

1 Answers1