add and get list in and from SharedPref android

/**
     *     Save and get ArrayList in SharedPreference
     */

    public void saveArrayList(ArrayList<String> list, String key){
        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(activity);
        SharedPreferences.Editor editor = prefs.edit();
        Gson gson = new Gson();
        String json = gson.toJson(list);
        editor.putString(key, json);
        editor.apply();     // This line is IMPORTANT !!!
    }

    public ArrayList<String> getArrayList(String key){
        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(activity);
        Gson gson = new Gson();
        String json = prefs.getString(key, null);
        Type type = new TypeToken<ArrayList<String>>() {}.getType();
        return gson.fromJson(json, type);
    }