RandomAccessFile多线程下载

public class DownloadServer {

    private int threadCount = 4;
    private static String fileUrl = "https://dldir1.qq.com/qqtv/mac/TencentVideo_V2.2.1.42253.dmg";
//    private static String fileUrl = "http://statics.garmentnet.cn/file/file_photo/show/news/5c3c055c5793d567739439.jpg";

    private static ExecutorService executorService = new ThreadPoolExecutor(4, 4, 180, TimeUnit.SECONDS, new LinkedBlockingQueue<>(10), new Download(), new ThreadPoolExecutor.DiscardPolicy());

    private static ScheduledExecutorService scheduledExecutorService = new ScheduledThreadPoolExecutor(1, new Download());

    private int getFileInfo() {
        int count = 0;
        try {
            URL url = new URL(fileUrl);
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            count = urlConnection.getContentLength();
            System.out.println(count);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return count;
    }


    private void download(int fileSize) throws IOException {
        File file = new File("d.dmg");
        if (file.exists()) {
            file.delete();
            file.createNewFile();
        }
        int perSize = fileSize / threadCount;
        int start;
        int end;
        for (int i = 0; i < threadCount; i++) {
            start = i * perSize;
            if (i == threadCount - 1) {
                end = fileSize - 1;
            } else {
                end = (i + 1) * perSize - 1;
            }

            executorService.execute(new Download(fileUrl, file, start, end));
        }
    }

    public static void main(String[] args) {
        DownloadServer downloadServer = new DownloadServer();
        int size = downloadServer.getFileInfo();
        scheduledExecutorService.scheduleAtFixedRate(new DownloadCount(size), 0, 10, TimeUnit.MILLISECONDS);
        try {
            downloadServer.download(size);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

public class Download implements Runnable, ThreadFactory {

    private String fileUrl;
    private File file;
    private int start;
    private int end;
    public static AtomicInteger downloadFileSize = new AtomicInteger(0);
    private static AtomicInteger threadNum = new AtomicInteger(0);

    public Download(){

    }

    public Download(String fileUrl, File file, int start, int end) {
        this.file = file;
        this.start = start;
        this.end = end;
        this.fileUrl = fileUrl;
    }

    @Override
    public void run() {
        try {
            URL url = new URL(fileUrl);
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestProperty("Range", "bytes=" + start + "-" + end);

            InputStream inputStream = httpURLConnection.getInputStream();
            RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
            randomAccessFile.seek(start);
            byte[] bytes = new byte[1024];
            int len = 0;
            while ((len = inputStream.read(bytes)) != -1) {
                randomAccessFile.write(bytes, 0, len);
                downloadFileSize.addAndGet(len);
//                System.out.println(Thread.currentThread().getName() + "-" + downloadFileSize.addAndGet(len));
            }
            randomAccessFile.close();

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public Thread newThread(Runnable r) {
        return new Thread(r, "Run-" + threadNum.incrementAndGet());
    }
}

public class DownloadCount implements Runnable {

    private int fileSize;
    public DownloadCount(int fileSize) {
        this.fileSize = fileSize;
    }

    @Override
    public void run() {
        if(fileSize != Download.downloadFileSize.get()) {
            System.out.println(Download.downloadFileSize);
        }
    }
}