public void update(String key, String oldValue, String newValue){

        if(dictionary.containsKey(key)){
            if(lookup(key).containsValue(oldValue)){

                List<String> tmp = new ArrayList<>();
                tmp = dictionary.get(key);
                tmp.remove(oldValue);
                tmp.add(newValue);

                dictionary.put(key, tmp);

            }
        }
    }