public static final Set fromMap(Map map, Object... keys) {
        if (keys != null && map != null) {
            Set answer = new HashSet();
            for (Object key : keys) {
                if (map.containsKey(key)) {
                    answer.add(map.get(key));
                }
            }
            return Collections.unmodifiableSet(answer);
        }
        return Collections.EMPTY_SET;
    }
public static final Set fromMap ( Map map , Object ... keys ) { if ( keys != null && map != null ) { Set answer = new HashSet ( ) ; for ( Object key : keys ) { if ( map . containsKey ( key ) ) { answer . add ( map . get ( key ) ) ; } } return Collections . unmodifiableSet ( answer ) ; } return Collections . EMPTY_SET ; }
Given a map and a set of keys, return a set containing the values referred-to by the keys.
If the map is null or the keys are null, the EMPTY_SET is returned.
If a passed key does not exist in the map, nothing is added to the set.
However, if the key is present and maps to null, null is added to the set.