### Question:
CodeSaver { static String clean(String user) { return user.replaceAll("[^\\dA-Za-z0-9@\\.]", "_"); }  static void save(String user, long date, int index, int count, String code); static SimpleDateFormat formatter; }### Answer:
@Test public void shouldCleanFileNameFromEmail() { assertEquals("qwe_asd_zxc_123@gmail.com", CodeSaver.clean("qwe*asd+zxc!123@gmail.com")); }