Util { public static boolean isNullOrEmpty(String s) { return s == null || s.isEmpty(); } private  Util(); static boolean isNullOrEmpty(String s); static void checkArgument(boolean condition); static void checkArgument(boolean condition, String error, Object arg1);  }
@Test public void testIsNullOrEmpty() throws Exception { assertThat(Util.isNullOrEmpty(null)).isTrue(); assertThat(Util.isNullOrEmpty("")).isTrue(); assertThat(Util.isNullOrEmpty("\0")).isFalse(); assertThat(Util.isNullOrEmpty("some text")).isFalse(); }