pdf转base64

public static String pdfToBase64() {
    InputStream is = null;
    ByteArrayOutputStream os = null;
    String dUrlData="";
    byte[] buff = new byte[1024];
    int len = 0;
    try {
        is = new FileInputStream(new File("C:\\Users\\Administrator\\Desktop\\文档\\接口文档-修改版.pdf"));
        os = new ByteArrayOutputStream();
        while ((len = is.read(buff)) != -1) {
            os.write(buff, 0, len);
        }
        os.flush();
        os.toByteArray();
        dUrlData = Base64.getEncoder().encodeToString(os.toByteArray());
    } catch (IOException e) {
    } finally {
        if (is != null) {
            try {
                is.close();
            } catch (IOException e) {}
        }
        if (os != null) {
            try {
                os.close();
            } catch (IOException e) {}
        }
    }
    return dUrlData;
}