### Question:
StringUtils { public static boolean isEquals(String s1, String s2) { if (s1 == null && s2 == null) return true; if (s1 == null || s2 == null) return false; return s1.equals(s2); }  static boolean isBlank(String str); static boolean isEmpty(String str); static boolean isNotEmpty(String str); static boolean isInteger(String str); static int parseInteger(String str); static Map<String, String> parseQueryString(String qs); static String getServiceKey(Map<String, String> ps); static String toQueryString(Map<String, String> ps); static boolean isEquals(String s1, String s2); static boolean isContains(String values, String value); static boolean isContains(String[] values, String value); static boolean isNumeric(String str); static final String[] EMPTY_STRING_ARRAY; }### Answer:
@Test public void isEquals() throws Exception { assertTrue(StringUtils.isEquals(null, null)); assertTrue(StringUtils.isEquals("", "")); assertTrue(StringUtils.isEquals("man", "man")); assertFalse(StringUtils.isEquals(null, "")); assertFalse(StringUtils.isEquals("man", "")); assertFalse(StringUtils.isEquals("man", "woman")); }