java下载图片并进行64位编码

public String GetUrlImageToBase64(String url) throws Exception {
        if (url == null || "".equals(url.trim()))
            return null;
        URL u = new URL(url);
        // 打开图片路径
        HttpURLConnection conn = (HttpURLConnection) u.openConnection();
        // 设置请求方式为GET
        conn.setRequestMethod("GET");
        // 设置超时响应时间为5秒
        conn.setConnectTimeout(5000);
        // 通过输入流获取图片数据
        InputStream inStream = conn.getInputStream();
        // 读取图片字节数组
        byte[] data = new byte[inStream.available()];
        inStream.read(data);
        inStream.close();
        // 返回Base64编码过的字节数组字符串
        String base64string = new String(Base64.encode(data));
        
        return base64string;
    }