Java中文件下载的下载百分比

Question

I got this code for downloading my files:

public static void download()
            throws MalformedURLException, IOException
    {
        BufferedInputStream in = null;
        FileOutputStream out = null;
        try
        {
            in = new BufferedInputStream(new URL("https://www.dropbox.com/s/1uff8eeujplz4sf/files.zip?dl=1").openStream());
            out = new FileOutputStream(System.getProperty("user.home") + "/Adasti/files.zip");
            byte data[] = new byte[1024];
            int count;

            while ((count = in.read(data, 0, 1024)) != -1)
            {
                out.write(data, 0, count);
            }
        } catch (MalformedURLException e1)
        {
            e1.printStackTrace();
        } catch (IOException e2)
        {
            e2.printStackTrace();
        } finally
        {
            if (in != null)
                in.close();
            if (out != null)
                out.close();
        }
    }

I want to print out the percentage of the download while its downloading. Is this possible with my method and if yes, how will I do it?

Answer 1

You have to get the file size before start the download. Be carefull, not always the server can give you the file size (for sample streaming or some file server). Try this:

/**
 * 
 * @param remotePath
 * @param localPath
 */
public static void download(String remotePath, String localPath) {
    BufferedInputStream in = null;
    FileOutputStream out = null;

    try {
        URL url = new URL(remotePath);
        URLConnection conn = url.openConnection();
        int size = conn.getContentLength();

        if (size < 0) {
            System.out.println("Could not get the file size");
        } else {
            System.out.println("File size: " + size);
        }

        in = new BufferedInputStream(url.openStream());
        out = new FileOutputStream(localPath);
        byte data[] = new byte[1024];
        int count;
        double sumCount = 0.0;

        while ((count = in.read(data, 0, 1024)) != -1) {
            out.write(data, 0, count);

            sumCount += count;
            if (size > 0) {
                System.out.println("Percentace: " + (sumCount / size * 100.0) + "%");
            }
        }

    } catch (MalformedURLException e1) {
        e1.printStackTrace();
    } catch (IOException e2) {
        e2.printStackTrace();
    } finally {
        if (in != null)
            try {
                in.close();
            } catch (IOException e3) {
                e3.printStackTrace();
            }
        if (out != null)
            try {
                out.close();
            } catch (IOException e4) {
                e4.printStackTrace();
            }
    }
}

The call to this method is something like this:

download("https://www.dropbox.com/s/1uff8eeujplz4sf/files.zip?dl=1", System.getProperty("user.home") + "/files.zip");