java线程池分段下载文件

目录

• • 一：实现基本的下载的功能
  • • 代码实现：
    • • 常量类：
      • http相关工具类
      • 日志工具类
      • 下载器
      • 测试类
  • 二：展示下载信息
  • • 代码实现
    • • 常量类
      • 文件类
      • http相关工具类
      • 日志工具类
      • 展示下载信息
      • 下载器
      • 测试类
  • 三：使用多线程分段下载
  • • 代码实现
    • • 常量类
      • 文件类
      • http相关工具类
      • 日志工具类
      • 展示下载信息
      • 分块载任务
      • 下载器
      • 测试类
  • 四：分段合并下载
  • • 代码实现：
    • • 常量类
      • 文件类
      • http相关工具类
      • 日志工具类
      • 分块载任务
      • 展示下载信息
      • 下载器
      • 测试类

一：实现基本的下载的功能

git链接：https://gitee.com/zhongbai111/multithreaded-block-download.git

代码实现： 常量类：

public class Constant {
    public static final String PATH = "E:\mytest\";
}

http相关工具类

public class HttpUtils {

    
    public static HttpURLConnection getHttpURLConnection(String url) throws IOException {
        URL httpUrl = new URL(url);
        HttpURLConnection httpURLConnection = (HttpURLConnection)httpUrl.openConnection();
        //向文件所在的服务器发送标识信息
        httpURLConnection.setRequestProperty("User-Agent","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/14.0.835.163 Safari/535.1");
        return httpURLConnection;
    }

    
    public static String getHttpFileName(String url) {
        int index = url.lastIndexOf("/");
        return url.substring(index + 1);
    }
}

日志工具类

public class LogUtils {

    public static void info(String msg, Object... args) {
        print(msg,"-info-",args);
    }

    public static void error(String msg, Object... args) {
        print(msg,"-error-",args);
    }

    private static void print(String msg, String level, Object... args) {
        if (args != null && args.length > 0) {
            msg = String.format(msg.replace("{}", "%s"), args);
        }
        String name = Thread.currentThread().getName();
        System.out.println(LocalTime.now().format(DateTimeFormatter.ofPattern("hh:mm:ss")) + " " + name + level + msg);
    }
}

下载器

public class Downloader {

    public void download(String url) {
        //获取文件名
        String httpFileName = HttpUtils.getHttpFileName(url);
        //文件下载路径
        httpFileName = Constant.PATH + httpFileName;

        //获取连接对象
        HttpURLConnection httpURLConnection = null;
        try {
            httpURLConnection = HttpUtils.getHttpURLConnection(url);
        } catch (IOException e) {
            e.printStackTrace();
        }

        try (
                InputStream input = httpURLConnection.getInputStream();
                BufferedInputStream bis = new BufferedInputStream(input);
                FileOutputStream fos = new FileOutputStream(httpFileName);
                BufferedOutputStream bos = new BufferedOutputStream(fos)
        ) {
            int len = -1;
            while ((len = bis.read()) != -1) {
                bos.write(len);
            }
        } catch (FileNotFoundException e) {
            LogUtils.error("下载的文件不存在{}",url);//下载的文件不存在abc
        } catch (Exception e) {
            LogUtils.error("下载失败");
        } finally {
            //关闭连接对象
            if (httpURLConnection != null) {
                httpURLConnection.disconnect();
            }
        }

    }
}

测试类

public class Main {
    public static void main(String[] args) {
        //下载地址
        String url = null;
        if (args == null || args.length == 0) {
            for (; ; ) {
                LogUtils.info("请输入下载地址");
                Scanner scanner = new Scanner(System.in);
                url = scanner.next();
                if (url != null) {
                    break;
                }
            }
        }else {
            url = args[0];
        }

        Downloader downloader = new Downloader();
        downloader.download(url);
    }
}

二：展示下载信息

代码实现 常量类

public class Constant {
    public static final String PATH = "E:\mytest\";

    public static final double MB = 1024d * 1024d;

    public static final int BYTE_SIZE = 1024 * 100;
}

文件类

public class FileUtils {

    
    public static long getFileContentLength(String path) {
        File file = new File(path);

        return file.exists() && file.isFile() ? file.length() : 0;
    }
}

http相关工具类

public class HttpUtils {

    
    public static HttpURLConnection getHttpURLConnection(String url) throws IOException {
        URL httpUrl = new URL(url);
        HttpURLConnection httpURLConnection = (HttpURLConnection)httpUrl.openConnection();
        //向文件所在的服务器发送标识信息
        httpURLConnection.setRequestProperty("User-Agent","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/14.0.835.163 Safari/535.1");
        return httpURLConnection;
    }

    
    public static String getHttpFileName(String url) {
        int index = url.lastIndexOf("/");
        return url.substring(index + 1);
    }
}

日志工具类

public class LogUtils {

    public static void info(String msg, Object... args) {
        print(msg,"-info-",args);
    }

    public static void error(String msg, Object... args) {
        print(msg,"-error-",args);
    }

    private static void print(String msg, String level, Object... args) {
        if (args != null && args.length > 0) {
            msg = String.format(msg.replace("{}", "%s"), args);
        }
        String name = Thread.currentThread().getName();
        System.out.println(LocalTime.now().format(DateTimeFormatter.ofPattern("hh:mm:ss")) + " " + name + level + msg);
    }
}

展示下载信息

public class DownloadInfoThread implements Runnable {

    //下载文件总大小
    private long httpFileContentLength;

    //本地已下载文件的大小，
    public double finishedSize;

    //本次累计下载的大小
    public volatile double downSize;

    //前一次下载的大小
    public double prevSize;

    public DownloadInfoThread(long httpFileContentLength) {
        this.httpFileContentLength = httpFileContentLength;
    }

    @Override
    public void run() {
        //计算文件总大小 单位：mb
        String httpFileSize = String.format("%.2f", httpFileContentLength / Constant.MB);

        //计算每秒下载速度 kb
        int speed = (int)((downSize - prevSize) / 1024d);
        prevSize = downSize;

        //剩余文件的大小
        double remainSize = httpFileContentLength - finishedSize - downSize;

        //计算剩余时间
        String remainTime = String.format("%.1f", remainSize / 1024d / speed);

        if ("Infinity".equalsIgnoreCase(remainTime)) {
            remainTime = "-";
        }

        //已下载大小
        String currentFileSize = String.format("%.2f", (downSize - finishedSize) / Constant.MB);

        String downInfo = String.format("已下载 %smb/%smb,速度 %skb/s,剩余时间 %ss",
                currentFileSize, httpFileSize, speed, remainTime);

        System.out.print("r");
        System.out.print(downInfo);

    }
}

下载器

public class Downloader {

    public ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(1);

    public void download(String url) {
        //获取文件名
        String httpFileName = HttpUtils.getHttpFileName(url);
        //文件下载路径
        httpFileName = Constant.PATH + httpFileName;

        //获取本地文件的大小
        long localFileLength = FileUtils.getFileContentLength(httpFileName);

        //获取连接对象
        HttpURLConnection httpURLConnection = null;
        DownloadInfoThread downloadInfoThread = null;
        try {
            httpURLConnection = HttpUtils.getHttpURLConnection(url);
            //获取下载文件的总大小
            int contentLength = httpURLConnection.getContentLength();

            //判断文件是否已下载过
            if (localFileLength >= contentLength) {
                LogUtils.info("{}已下载完毕，无需重新下载",httpFileName);
                return;
            }

            //创建获取下载信息的任务对象
            downloadInfoThread = new DownloadInfoThread(contentLength);
            //将任务交给线程执行，每隔1秒执行一次
            scheduledExecutorService.scheduleAtFixedRate(downloadInfoThread,1,1, TimeUnit.SECONDS);

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

        try (
                InputStream input = httpURLConnection.getInputStream();
                BufferedInputStream bis = new BufferedInputStream(input);
                FileOutputStream fos = new FileOutputStream(httpFileName);
                BufferedOutputStream bos = new BufferedOutputStream(fos)
        ) {
            int len = -1;
            byte[] buffer = new byte[Constant.BYTE_SIZE];
            while ((len = bis.read(buffer)) != -1) {
                downloadInfoThread.downSize += len;
                bos.write(buffer,0,len);
            }
        } catch (FileNotFoundException e) {
            LogUtils.error("下载的文件不存在{}",url);//下载的文件不存在abc
        } catch (Exception e) {
            LogUtils.error("下载失败");
        } finally {
            System.out.print("r");
            System.out.print("下载完成");
            //关闭连接对象
            if (httpURLConnection != null) {
                httpURLConnection.disconnect();
            }

            //关闭
            scheduledExecutorService.shutdownNow();
        }

    }
}

测试类

public class Main {
    public static void main(String[] args) {
        //下载地址
        String url = null;
        if (args == null || args.length == 0) {
            for (; ; ) {
                LogUtils.info("请输入下载地址");
                Scanner scanner = new Scanner(System.in);
                url = scanner.next();
                if (url != null) {
                    break;
                }
            }
        }else {
            url = args[0];
        }

        Downloader downloader = new Downloader();
        downloader.download(url);
    }
}

三：使用多线程分段下载

代码实现 常量类

public class Constant {
    public static final String PATH = "E:\mytest\";

    public static final double MB = 1024d * 1024d;

    public static final int BYTE_SIZE = 1024 * 100;

    //线程数量
    public static final int THREAD_NUM = 5;
}

文件类

public class FileUtils {

    
    public static long getFileContentLength(String path) {
        File file = new File(path);

        return file.exists() && file.isFile() ? file.length() : 0;
    }
}

http相关工具类

public class HttpUtils {

    
    public static long getHttpFileContentLength(String url) throws IOException {
        int contentLength;
        HttpURLConnection httpURLConnection = null;
        try {
            httpURLConnection = getHttpURLConnection(url);
            contentLength = httpURLConnection.getContentLength();
        } finally {
            if (httpURLConnection != null) {
                httpURLConnection.disconnect();
            }
        }
        return contentLength;
    }

    
    public static HttpURLConnection getHttpURLConnection(String url, long startPos, long endPos) throws IOException {
        HttpURLConnection httpURLConnection = getHttpURLConnection(url);
        LogUtils.info("下载的区间是：{}-{}",startPos,endPos);

        if (endPos != 0) {
            httpURLConnection.setRequestProperty("RANGE","bytes="+startPos + "-" + endPos);
        }else {
            httpURLConnection.setRequestProperty("RANGE","bytes="+startPos + "-");
        }

        return httpURLConnection;
    }

    
    public static HttpURLConnection getHttpURLConnection(String url) throws IOException {
        URL httpUrl = new URL(url);
        HttpURLConnection httpURLConnection = (HttpURLConnection)httpUrl.openConnection();
        //向文件所在的服务器发送标识信息
        httpURLConnection.setRequestProperty("User-Agent","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/14.0.835.163 Safari/535.1");
        return httpURLConnection;
    }

    
    public static String getHttpFileName(String url) {
        int index = url.lastIndexOf("/");
        return url.substring(index + 1);
    }
}

日志工具类

public class LogUtils {

    public static void info(String msg, Object... args) {
        print(msg,"-info-",args);
    }

    public static void error(String msg, Object... args) {
        print(msg,"-error-",args);
    }

    private static void print(String msg, String level, Object... args) {
        if (args != null && args.length > 0) {
            msg = String.format(msg.replace("{}", "%s"), args);
        }
        String name = Thread.currentThread().getName();
        System.out.println(LocalTime.now().format(DateTimeFormatter.ofPattern("hh:mm:ss")) + " " + name + level + msg);
    }
}

展示下载信息

public class DownloadInfoThread implements Runnable {

    //下载文件总大小
    private long httpFileContentLength;

    //本地已下载文件的大小，
    public static LongAdder finishedSize = new LongAdder();

    //本次累计下载的大小
    public static volatile LongAdder downSize = new LongAdder();

    //前一次下载的大小
    public double prevSize;

    public DownloadInfoThread(long httpFileContentLength) {
        this.httpFileContentLength = httpFileContentLength;
    }

    @Override
    public void run() {
        //计算文件总大小 单位：mb
        String httpFileSize = String.format("%.2f", httpFileContentLength / Constant.MB);

        //计算每秒下载速度 kb
        int speed = (int)((downSize.doublevalue() - prevSize) / 1024d);
        prevSize = downSize.doublevalue();

        //剩余文件的大小
        double remainSize = httpFileContentLength - finishedSize.doublevalue() - downSize.doublevalue();

        //计算剩余时间
        String remainTime = String.format("%.1f", remainSize / 1024d / speed);

        if ("Infinity".equalsIgnoreCase(remainTime)) {
            remainTime = "-";
        }

        //已下载大小
        String currentFileSize = String.format("%.2f", (downSize.doublevalue() - finishedSize.doublevalue()) / Constant.MB);

        String downInfo = String.format("已下载 %smb/%smb,速度 %skb/s,剩余时间 %ss",
                currentFileSize, httpFileSize, speed, remainTime);

        System.out.print("r");
        System.out.print(downInfo);

    }
}

分块载任务

public class DownloaderTask implements Callable {

    private String url;

    //下载的起始位置
    private long startPos;

    //下载的结束位置
    private long endPos;

    //标识当前是哪一部分
    private int part;

    public DownloaderTask(String url, long startPos, long endPos, int part) {
        this.url = url;
        this.startPos = startPos;
        this.endPos = endPos;
        this.part = part;
    }

    @Override
    public Boolean call() throws Exception {
        //获取文件名
        String httpFileName = HttpUtils.getHttpFileName(url);
        //分块的文件名
        httpFileName = httpFileName + ".temp" + part;
        //下载路径
        httpFileName = Constant.PATH + httpFileName;

        //获取分块下载的连接
        HttpURLConnection httpURLConnection = HttpUtils.getHttpURLConnection(url, startPos, endPos);

        try (
                InputStream input = httpURLConnection.getInputStream();
                BufferedInputStream bis = new BufferedInputStream(input);
                RandomAccessFile accessFile = new RandomAccessFile(httpFileName, "rw")
        ) {
            byte[] buffer = new byte[Constant.BYTE_SIZE];
            int len = -1;
            //循环读取数据
            while ((len = bis.read(buffer)) != -1) {
                //1秒内下载数据之和, 通过原子类进行操作
                DownloadInfoThread.downSize.add(len);
                accessFile.write(buffer,0,len);
            }
        } catch (FileNotFoundException e) {
            LogUtils.error("下载文件不存在{}", url);
            return false;
        } catch (Exception e) {
            LogUtils.error("下载出现异常");
            return false;
        } finally {
            httpURLConnection.disconnect();
        }

        return true;
    }
}

下载器

public class Downloader {

    public ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(1);
    //线程池对象
    public ThreadPoolExecutor poolExecutor = new ThreadPoolExecutor(Constant.THREAD_NUM, Constant.THREAD_NUM, 0, TimeUnit.SECONDS, new ArrayBlockingQueue<>(Constant.THREAD_NUM));

    public void download(String url) {
        //获取文件名
        String httpFileName = HttpUtils.getHttpFileName(url);
        //文件下载路径
        httpFileName = Constant.PATH + httpFileName;

        //获取本地文件的大小
        long localFileLength = FileUtils.getFileContentLength(httpFileName);

        //获取连接对象
        HttpURLConnection httpURLConnection = null;
        DownloadInfoThread downloadInfoThread = null;
        try {
            httpURLConnection = HttpUtils.getHttpURLConnection(url);
            //获取下载文件的总大小
            int contentLength = httpURLConnection.getContentLength();

            //判断文件是否已下载过
            if (localFileLength >= contentLength) {
                LogUtils.info("{}已下载完毕，无需重新下载",httpFileName);
                return;
            }

            //创建获取下载信息的任务对象
            downloadInfoThread = new DownloadInfoThread(contentLength);
            //将任务交给线程执行，每隔1秒执行一次
            scheduledExecutorService.scheduleAtFixedRate(downloadInfoThread,1,1, TimeUnit.SECONDS);

            //切分任务
            ArrayList list = new ArrayList<>();
            spilt(url, list);

            list.forEach(future -> {
                try {
                    future.get();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (ExecutionException e) {
                    e.printStackTrace();
                }
            });

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            System.out.print("r");
            System.out.print("下载完成");
            //关闭连接对象
            if (httpURLConnection != null) {
                httpURLConnection.disconnect();
            }

            //关闭
            scheduledExecutorService.shutdownNow();

            //关闭线程池
            poolExecutor.shutdown();
        }

    }

    
    public void spilt(String url, ArrayList futureList) {

        try {
            //获取下载文件大小
            long contentLength = HttpUtils.getHttpFileContentLength(url);

            //计算切分后的文件大小
            long size = contentLength / Constant.THREAD_NUM;

            //计算分块个数
            for (int i = 0; i < Constant.THREAD_NUM; i++) {
                //计算下载起始位置
                long startPos = i * size;
                //计算结束位置
                long endPos;

                if (i == Constant.THREAD_NUM - 1) {
                    //下载最后一块，下载剩余的部分
                    endPos = 0;
                }else {
                    endPos = startPos + size;
                }

                //如果不是第一块，起始位置要+1
                if (startPos != 0) {
                    startPos++;
                }

                //创建任务对象
                DownloaderTask downloaderTask = new DownloaderTask(url, startPos, endPos,i);

                //将任务提交到线程池中
                Future future = poolExecutor.submit(downloaderTask);

                futureList.add(future);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

测试类

public class Main {
    public static void main(String[] args) {
        //下载地址
        String url = null;
        if (args == null || args.length == 0) {
            for (; ; ) {
                LogUtils.info("请输入下载地址");
                Scanner scanner = new Scanner(System.in);
                url = scanner.next();
                if (url != null) {
                    break;
                }
            }
        }else {
            url = args[0];
        }

        Downloader downloader = new Downloader();
        downloader.download(url);
    }
}

四：分段合并下载

代码实现： 常量类

public class Constant {
    public static final String PATH = "E:\mytest\";

    public static final double MB = 1024d * 1024d;

    public static final int BYTE_SIZE = 1024 * 100;

    //线程数量
    public static final int THREAD_NUM = 5;
}

文件类

public class FileUtils {

    
    public static long getFileContentLength(String path) {
        File file = new File(path);

        return file.exists() && file.isFile() ? file.length() : 0;
    }
}

http相关工具类

public class HttpUtils {

    
    public static long getHttpFileContentLength(String url) throws IOException {
        int contentLength;
        HttpURLConnection httpURLConnection = null;
        try {
            httpURLConnection = getHttpURLConnection(url);
            contentLength = httpURLConnection.getContentLength();
        } finally {
            if (httpURLConnection != null) {
                httpURLConnection.disconnect();
            }
        }
        return contentLength;
    }

    
    public static HttpURLConnection getHttpURLConnection(String url, long startPos, long endPos) throws IOException {
        HttpURLConnection httpURLConnection = getHttpURLConnection(url);
        LogUtils.info("下载的区间是：{}-{}",startPos,endPos);

        if (endPos != 0) {
            httpURLConnection.setRequestProperty("RANGE","bytes="+startPos + "-" + endPos);
        }else {
            httpURLConnection.setRequestProperty("RANGE","bytes="+startPos + "-");
        }

        return httpURLConnection;
    }

    
    public static HttpURLConnection getHttpURLConnection(String url) throws IOException {
        URL httpUrl = new URL(url);
        HttpURLConnection httpURLConnection = (HttpURLConnection)httpUrl.openConnection();
        //向文件所在的服务器发送标识信息
        httpURLConnection.setRequestProperty("User-Agent","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/14.0.835.163 Safari/535.1");
        return httpURLConnection;
    }

    
    public static String getHttpFileName(String url) {
        int index = url.lastIndexOf("/");
        return url.substring(index + 1);
    }
}

日志工具类

public class LogUtils {

    public static void info(String msg, Object... args) {
        print(msg,"-info-",args);
    }

    public static void error(String msg, Object... args) {
        print(msg,"-error-",args);
    }

    private static void print(String msg, String level, Object... args) {
        if (args != null && args.length > 0) {
            msg = String.format(msg.replace("{}", "%s"), args);
        }
        String name = Thread.currentThread().getName();
        System.out.println(LocalTime.now().format(DateTimeFormatter.ofPattern("hh:mm:ss")) + " " + name + level + msg);
    }
}

分块载任务

public class DownloaderTask implements Callable {

    private String url;

    //下载的起始位置
    private long startPos;

    //下载的结束位置
    private long endPos;

    //标识当前是哪一部分
    private int part;

    private CountDownLatch countDownLatch;

    public DownloaderTask(String url, long startPos, long endPos, int part, CountDownLatch countDownLatch) {
        this.url = url;
        this.startPos = startPos;
        this.endPos = endPos;
        this.part = part;
        this.countDownLatch = countDownLatch;
    }

    @Override
    public Boolean call() throws Exception {
        //获取文件名
        String httpFileName = HttpUtils.getHttpFileName(url);
        //分块的文件名
        httpFileName = httpFileName + ".temp" + part;
        //下载路径
        httpFileName = Constant.PATH + httpFileName;

        //获取分块下载的连接
        HttpURLConnection httpURLConnection = HttpUtils.getHttpURLConnection(url, startPos, endPos);

        try (
                InputStream input = httpURLConnection.getInputStream();
                BufferedInputStream bis = new BufferedInputStream(input);
                RandomAccessFile accessFile = new RandomAccessFile(httpFileName, "rw")
        ) {
            byte[] buffer = new byte[Constant.BYTE_SIZE];
            int len = -1;
            //循环读取数据
            while ((len = bis.read(buffer)) != -1) {
                //1秒内下载数据之和, 通过原子类进行操作
                DownloadInfoThread.downSize.add(len);
                accessFile.write(buffer,0,len);
            }
        } catch (FileNotFoundException e) {
            LogUtils.error("下载文件不存在{}", url);
            return false;
        } catch (Exception e) {
            LogUtils.error("下载出现异常");
            return false;
        } finally {
            httpURLConnection.disconnect();
            //如果减到了0，则会唤醒所有等待在这个latch上的线程。
            countDownLatch.countDown();
        }

        return true;
    }
}

展示下载信息

public class DownloadInfoThread implements Runnable {

    //下载文件总大小
    private long httpFileContentLength;

    //本地已下载文件的大小，
    public static LongAdder finishedSize = new LongAdder();

    //本次累计下载的大小  LongAdder保证共享数据的原子性
    public static volatile LongAdder downSize = new LongAdder();

    //前一次下载的大小
    public double prevSize;

    public DownloadInfoThread(long httpFileContentLength) {
        this.httpFileContentLength = httpFileContentLength;
    }

    @Override
    public void run() {
        //计算文件总大小 单位：mb
        String httpFileSize = String.format("%.2f", httpFileContentLength / Constant.MB);

        //计算每秒下载速度 kb
        int speed = (int)((downSize.doublevalue() - prevSize) / 1024d);
        prevSize = downSize.doublevalue();

        //剩余文件的大小
        double remainSize = httpFileContentLength - finishedSize.doublevalue() - downSize.doublevalue();

        //计算剩余时间
        String remainTime = String.format("%.1f", remainSize / 1024d / speed);

        if ("Infinity".equalsIgnoreCase(remainTime)) {
            remainTime = "-";
        }

        //已下载大小
        String currentFileSize = String.format("%.2f", (downSize.doublevalue() - finishedSize.doublevalue()) / Constant.MB);

        String downInfo = String.format("已下载 %smb/%smb,速度 %skb/s,剩余时间 %ss",
                currentFileSize, httpFileSize, speed, remainTime);

        System.out.print("r");
        System.out.print(downInfo);

    }
}

下载器

public class Downloader {

    public ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(1);
    //线程池对象
    public ThreadPoolExecutor poolExecutor = new ThreadPoolExecutor(Constant.THREAD_NUM, Constant.THREAD_NUM, 0, TimeUnit.SECONDS, new ArrayBlockingQueue<>(Constant.THREAD_NUM));

    private CountDownLatch countDownLatch = new CountDownLatch(Constant.THREAD_NUM);

    public void download(String url) {
        //获取文件名
        String httpFileName = HttpUtils.getHttpFileName(url);
        //文件下载路径
        httpFileName = Constant.PATH + httpFileName;

        //获取本地文件的大小
        long localFileLength = FileUtils.getFileContentLength(httpFileName);

        //获取连接对象
        HttpURLConnection httpURLConnection = null;
        DownloadInfoThread downloadInfoThread = null;
        try {
            httpURLConnection = HttpUtils.getHttpURLConnection(url);
            //获取下载文件的总大小
            int contentLength = httpURLConnection.getContentLength();

            //判断文件是否已下载过
            if (localFileLength >= contentLength) {
                LogUtils.info("{}已下载完毕，无需重新下载",httpFileName);
                return;
            }

            //创建获取下载信息的任务对象
            downloadInfoThread = new DownloadInfoThread(contentLength);
            //将任务交给线程执行，每隔1秒执行一次
            scheduledExecutorService.scheduleAtFixedRate(downloadInfoThread,1,1, TimeUnit.SECONDS);

            //切分任务
            ArrayList list = new ArrayList<>();
            spilt(url, list);

            //使当前线程进入同步队列进行等待，直到latch的值被减到0或者当前线程被中断，当前线程就会被唤醒。
            countDownLatch.await();

            //合并文件
            if (merge(httpFileName)) {
                //清除临时文件
                clearTemp(httpFileName);
            }

        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            System.out.print("r");
            System.out.print("下载完成");
            //关闭连接对象
            if (httpURLConnection != null) {
                httpURLConnection.disconnect();
            }

            //关闭
            scheduledExecutorService.shutdownNow();

            //关闭线程池
            poolExecutor.shutdown();
        }

    }

    
    public void spilt(String url, ArrayList futureList) {

        try {
            //获取下载文件大小
            long contentLength = HttpUtils.getHttpFileContentLength(url);

            //计算切分后的文件大小
            long size = contentLength / Constant.THREAD_NUM;

            //计算分块个数
            for (int i = 0; i < Constant.THREAD_NUM; i++) {
                //计算下载起始位置
                long startPos = i * size;
                //计算结束位置
                long endPos;

                if (i == Constant.THREAD_NUM - 1) {
                    //下载最后一块，下载剩余的部分
                    endPos = 0;
                }else {
                    endPos = startPos + size;
                }

                //如果不是第一块，起始位置要+1
                if (startPos != 0) {
                    startPos++;
                }

                //创建任务对象
                DownloaderTask downloaderTask = new DownloaderTask(url, startPos, endPos,i,countDownLatch);

                //将任务提交到线程池中
                Future future = poolExecutor.submit(downloaderTask);

                futureList.add(future);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    
    public boolean merge(String fileName) {
        LogUtils.info("开始合并文件{}", fileName);
        byte[] buffer = new byte[Constant.BYTE_SIZE];
        int len = -1;
        try (RandomAccessFile accessFile = new RandomAccessFile(fileName, "rw")) {
            for (int i = 0; i < Constant.THREAD_NUM ; i++) {
                try(BufferedInputStream bis = new BufferedInputStream(new FileInputStream(fileName + ".temp" + i))) {
                    while ((len = bis.read(buffer)) != -1) {
                        accessFile.write(buffer,0,len);
                    }
                }
            }
            LogUtils.info("文件合并完毕{}" + fileName);
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }

        return true;
    }

    
    public boolean clearTemp(String fileName) {
        for (int i = 0; i < Constant.THREAD_NUM; i++) {
            File file = new File(fileName + ".temp" + i);
            file.delete();
        }

        return true;
    }
}

测试类

public class Main {
    public static void main(String[] args) {
        //下载地址
        String url = null;
        if (args == null || args.length == 0) {
            for (; ; ) {
                LogUtils.info("请输入下载地址");
                Scanner scanner = new Scanner(System.in);
                url = scanner.next();
                if (url != null) {
                    break;
                }
            }
        }else {
            url = args[0];
        }

        Downloader downloader = new Downloader();
        downloader.download(url);
    }
}