HttpURLConnection从链接下载数据存放本地临时文件，Java

    private File download(String url) throws Exception {
        HttpURLConnection connection = getConnection(url);

        int contentLength = connection.getContentLength();

        String msg = connection.getResponseMessage();
        System.out.println(msg);

        InputStream is = connection.getInputStream();
        BufferedInputStream bis = new BufferedInputStream(is);
        File tempFile = File.createTempFile(UUID.randomUUID().toString(), "");
        FileOutputStream fos = new FileOutputStream(tempFile);
        BufferedOutputStream bos = new BufferedOutputStream(fos);

        int c;
        int count = 0;
        byte[] buf = new byte[1024 * 4];
        double pcent;
        while (true) {
            c = bis.read(buf);
            if (c == -1)
                break;
            bos.write(buf, 0, c);

            count = count + c;

            pcent = (count / (double) contentLength) * 100;
            System.out.print("已下载:" + String.format("%.2f", pcent) + "% \r");
        }

        bis.close();
        bos.close();
        fos.close();

        return tempFile;
    }

    private HttpURLConnection getConnection(String u) throws Exception {
        URL url = new URL(u);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestProperty("Connection", "Keep-Alive");
        connection.connect();

        return connection;
    }