### Question:
StringUtils { public static boolean isEmpty(String str) { return str == null || str.trim().isEmpty(); } private  StringUtils(); static double getDifference(String first, String second); static boolean containsAny(String str, Iterable<String> pieces); static boolean isEmpty(String str); static String formatException(Throwable th); static boolean isInsideString(char needle, String haystack);  }### Answer:
@Test public void shouldCheckIsEmptyUtil() { assertTrue(StringUtils.isEmpty(null)); assertTrue(StringUtils.isEmpty("")); assertTrue(StringUtils.isEmpty(" \t")); assertFalse(StringUtils.isEmpty("P")); assertFalse(StringUtils.isEmpty(" test")); }