### Question:
StringUtils { public static boolean isEmpty(String str) { return str == null || str.trim().length() == 0; }  static boolean isEmpty(String str); static boolean isSameStr(String a, String b); static String setToStr(Set<String> stringSet, String delimiter); static String setToStr(Set<String> stringSet, String delimiter, String defaultRet); static Set<String> strToSet(String str, String delimiter); static List<String> strToList(String str, String delimiter); static boolean startWithToLowerCase(String thisString, String anotherString); static final String EMPTY_STRING; static final int CHAR_A; static final int CHAR_Z; static final int CASE_GAP; }### Answer:
@Test public void testEmpty() { Assert.assertTrue(StringUtils.isEmpty("")); Assert.assertTrue(StringUtils.isEmpty(null)); Assert.assertFalse(StringUtils.isEmpty("aaa")); }