How to resume downloading files and show the progress in java

Question

I want to code a way to resume the download file in Java and show the progress if possible.

The following code was used to subtract the total size of the downloaded file (totalSize - downloaded) instead of completing the download.

URL url = new URL(urlFile);
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            File SDCardRoot = Environment.getExternalStorageDirectory();
            file = new File(SDCardRoot,"/MySchool/"+Folder+"/"+nameBook.getText().toString()+".pdf");
            urlConnection.setRequestProperty("Range", "bytes=" + file.length() + "-");
            urlConnection.setDoOutput(true);
            urlConnection.connect();
            outputStream = new FileOutputStream(file);
            InputStream inputStream = urlConnection.getInputStream();
            //this is the total size of the file which we are downloading
            totalSize = urlConnection.getContentLength();

            byte[] buffer = new byte[1024];
            int bufferLength = 0;

            while ( (bufferLength = inputStream.read(buffer)) > 0 ) {
                outputStream.write(buffer, 0, bufferLength);
                downloadedSize += bufferLength;
                }
            outputStream.close();

Answer 1

This might be useful for pause and resume but please specify exact problem.

if (outputFileCache.exists())
    {
        connection.setAllowUserInteraction(true);
        connection.setRequestProperty("Range", "bytes=" + outputFileCache.length() + "-");
    }

    connection.setConnectTimeout(14000);
    connection.setReadTimeout(20000);
    connection.connect();

    if (connection.getResponseCode() / 100 != 2)
        throw new Exception("Invalid response code!");
    else
    {
        String connectionField = connection.getHeaderField("content-range");

        if (connectionField != null)
        {
            String[] connectionRanges = connectionField.substring("bytes=".length()).split("-");
            downloadedSize = Long.valueOf(connectionRanges[0]);
        }

        if (connectionField == null && outputFileCache.exists())
            outputFileCache.delete();

        fileLength = connection.getContentLength() + downloadedSize;
        input = new BufferedInputStream(connection.getInputStream());
        output = new RandomAccessFile(outputFileCache, "rw");
        output.seek(downloadedSize);

        byte data[] = new byte[1024];
        int count = 0;
        int __progress = 0;

        while ((count = input.read(data, 0, 1024)) != -1 
                && __progress != 100) 
        {
            downloadedSize += count;
            output.write(data, 0, count);
            __progress = (int) ((downloadedSize * 100) / fileLength);
        }

        output.close();
        input.close();
   }