public FileReaderForCharSet(String fileName,String charSetName) throws FileNotFoundException, UnsupportedEncodingException {
  super(new FileInputStream(fileName),charSetName);
}

------解决方案--------------------
探讨

系统平台默认编码

可以这样设置编码：
BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream("xxx"), "UTF-8"));