code: public static String reverse(String str) {
        if (str == null) {
            return null;
        }
        return new StringBuffer(str).reverse().toString();
    }
docs: <p>Reverses a String as per {@link StringBuffer#reverse()}.</p>
  
  <p>A <code>null</code> String returns <code>null</code>.</p>
  
  <pre>
  GosuStringUtil.reverse(null)  = null
  GosuStringUtil.reverse("")    = ""
  GosuStringUtil.reverse("bat") = "tab"
  </pre>
  
  @param str  the String to reverse, may be null
  @return the reversed String, <code>null</code> if null String input