question: public static < K , V > MultiValueMap < K , V > unmodifiableMultiValueMap ( MultiValueMap < ? extends K , ? extends V > map ) { Assert . notNull ( map , "'map' must not be null" ) ; Map < K , List < V > > result = new LinkedHashMap < K , List < V > > ( map . size ( ) ) ; for ( Map . Entry < ? extends K , ? extends List < ? extends V > > entry : map . entrySet ( ) ) { List < V > values = Collections . unmodifiableList ( entry . getValue ( ) ) ; result . put ( entry . getKey ( ) , values ) ; } Map < K , List < V > > unmodifiableMap = Collections . unmodifiableMap ( result ) ; return toMultiValueMap ( unmodifiableMap ) ; }
target:  Return an unmodifiable view of the specified multi-value map.