code: public static String defaultString(String str, String defaultStr) {
        return str == null ? defaultStr : str;
    }
docs: <p>Returns either the passed in String, or if the String is
  <code>null</code>, the value of <code>defaultStr</code>.</p>
  
  <pre>
  GosuStringUtil.defaultString(null, "NULL")  = "NULL"
  GosuStringUtil.defaultString("", "NULL")    = ""
  GosuStringUtil.defaultString("bat", "NULL") = "bat"
  </pre>
  
  @see String#valueOf(Object)
  @param str  the String to check, may be null
  @param defaultStr  the default String to return
  if the input is <code>null</code>, may be null
  @return the passed in String, or the default if it was <code>null</code>