Strings { public static boolean isEmpty(String s) { return s == null || s.isEmpty(); }  static String join(Iterable<?> col, String separator); static boolean isBlank(String s); static boolean isNotBlank(String s); static boolean isEmpty(String s); static boolean isNotEmpty(String s); static List<String> splitAndTrim(String value, String regex); static String trim(String s); static String trimToNull(String s); static String joinClassNames(Iterable<?> iterable); static Boolean toBoolean(String s);  }
@Test void testIsEmpty() { assertTrue(Strings.isEmpty(null)); assertTrue(Strings.isEmpty("")); assertFalse(Strings.isEmpty(" ")); assertFalse(Strings.isEmpty("foo")); }