java 读取 utf-8 bom 出现乱码

private static String ReadUTF8WithBOMToString(String filePath) throws IOException
{
    String defaultEncoding = "UTF-8";
    InputStream inputStream = new FileInputStream(filePath);
    StringBuffer fileData = new StringBuffer();
    
    try {
        BOMInputStream bOMInputStream = new BOMInputStream(inputStream);
        ByteOrderMark bom = bOMInputStream.getBOM();
        String charsetName = bom == null ? defaultEncoding : bom.getCharsetName();
        InputStreamReader isr = new InputStreamReader(new BufferedInputStream(bOMInputStream), charsetName);
        BufferedReader reader = new BufferedReader(isr);
        char[] buf = new char[1024];
        int numRead = 0;
        while((numRead=reader.read(buf)) != -1)
        {
            String readData = String.valueOf(buf, 0, numRead);
            fileData.append(readData);
        }
        reader.close();
        return fileData.toString();
    } finally {
        inputStream.close();
    }
}

用到了一个jar包 Apache Commons IO，  https://img2020.cnblogs.com/blog/65667/202008/65667-20200812160049507-807397496.jpg，将图片链接下载后改名为 commons-io-2.7.jar