### Question:
Strings { public static boolean isNullOrEmpty(String s) { return s == null || s.isEmpty(); } private  Strings(); static int[] codePoints(String s); static boolean isNullOrEmpty(String s); static String nullToEmpty(String value); static String sanitizeWhitespace(String str);  }### Answer:
@Test public void isNullOrEmpty() { assertTrue(Strings.isNullOrEmpty(null)); assertTrue(Strings.isNullOrEmpty("")); assertFalse(Strings.isNullOrEmpty("a")); }