MainActivity.java

//Here is the mount drive function which I called in onCreate of my activity.

 private void mountDrive() throws IOException, InterruptedException {
        Process mProcess = Runtime.getRuntime().exec("/system/xbin/su");
        BufferedReader reader = new BufferedReader(new InputStreamReader(mProcess.getInputStream()));

        DataOutputStream dos = new DataOutputStream(mProcess.getOutputStream());
        dos.writeBytes("mkdir /mnt/usb\n");
        dos.flush();
        dos.writeBytes("mount -t vfat -o rw /dev/block/sda1 /mnt/usb\n");
        dos.flush();
        dos.writeBytes("exit\n");

        //Read the response
        String line, result = "";
        while ((line = reader.readLine()) != null) {
            result += line;
            Log.d("CMD","RESULT:"+result);
        }
        reader.close();
        dos.flush();
        dos.close();

        mProcess.waitFor();
    }