Strings { public static boolean isEmpty(final String s) { return isNull(s) || s.isEmpty(); } private  Strings(); static boolean isNull(final String s); static boolean isEmpty(final String s); static boolean isNotEmpty(final String s); static boolean isBlank(final String s); static String trim(final String s); static String trimToNull(final String s); static String trimToEmpty(final String s); static String toLowerCase(final String s);  }
@Test public void testIsEmpty() { final String nullString = null; final String emptyString = ""; final String blankString = " "; final String string = "a"; assertThat(Strings.isEmpty(nullString), is(true)); assertThat(Strings.isEmpty(emptyString), is(true)); assertThat(Strings.isEmpty(blankString), is(false)); assertThat(Strings.isEmpty(string), is(false)); }