### Question:
RegexUtil { public static boolean isEmail(String mail) { return mail.matches(mailRegex); }  static boolean isEmail(String mail); static final String mailRegex; }### Answer:
@Test public void check_for_valid_email() { String email = "zafeiris@aueb.gr"; Assert.assertTrue(RegexUtil.isEmail(email)); }
@Test public void check_for_invalid_email() { String email = "dsafewreg@"; Assert.assertFalse(RegexUtil.isEmail(email)); }