BASE64解析乱码问题

 public String base64Decoder(String str) {
        BASE64Decoder decode = new BASE64Decoder();
        String result = "";
        byte[] b;
        try {
            b = decode.decodeBuffer(str);
            result = new String(b,"utf-8");//切记此处千万不要用UTF-8
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }