Download File using MutilThread in java. Mấu chốt là dùng thằng conn.setRequestProperty("Range", "bytes=" + byteRange)

Downloader.java

package com.huantt.downloader;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

/**
 * Created by Huan on 7/5/2016.
 */
public class Downloader implements Runnable {
    private static org.apache.log4j.Logger log = org.apache.log4j.Logger.getLogger(Downloader.class);
    private BufferedInputStream bis;
    private RandomAccessFile bos;
    private String link;
    private String path;
    private File file;
    private int start;
    private int end;

    public Downloader(String link, String path, File file, int start, int end) {
        this.link = link;
        this.path = path;
        this.start = start;
        this.end = end;
        this.file = file;
    }

    @Override
    public void run() {
        URL url = null;
        try {
            url = new URL(link);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            String byteRange = start + "-" + end;
            connection.setRequestProperty("Range", "bytes=" + byteRange);
            connection.connect();

            bis = new BufferedInputStream(connection.getInputStream());

            bos = new RandomAccessFile(file, "rw");
            bos.seek(start);
            byte[] bytes = new byte[1024];
            int length;
            int downloaded = start;
            try {
                while (downloaded <= end) {
                    length = bis.read(bytes);
                    downloaded += length;
                    if (length != -1) {
                        bos.write(bytes, 0, length);
                    } else break;
                    log.info("Downloaded : " + downloaded);
                }
                bos.close();
                log.info("Finish !");
                log.info("Downloaded : " + downloaded);
            } catch (MalformedURLException e) {
                log.error(e.toString());
            } catch (IOException e) {
                log.error(e.toString());
            }
        } catch (IOException e) {
            log.error(e.toString());
        }

    }
}

DownloadManager.java

package com.huantt.downloader;

import java.io.File;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Created by Huan on 7/6/2016.
 */
public class DownloadManager implements Runnable {
    private static org.apache.log4j.Logger log = org.apache.log4j.Logger.getLogger(Downloader.class);

    int numOfThread;
    private String link;
    private String path;
    private String fileName;
    private static ExecutorService pool = Executors.newCachedThreadPool();

    public DownloadManager(int numOfThread, String link, String path, String fileName) {
        this.numOfThread = numOfThread;
        this.link = link;
        this.path = path;
        this.fileName = fileName + getFormatFile();
    }

    public DownloadManager(int numOfThread, String link, String path) {
        this.numOfThread = numOfThread;
        this.link = link;
        this.path = path;
        this.fileName = getFileName();
    }

    private String getFileName() {
        return new String(link.substring(link.lastIndexOf('/') + 1));
    }

    private String getFormatFile() {
        String format = "";
        if (link.lastIndexOf(".") != -1) {
            format = link.substring(link.lastIndexOf("."));
        }
        return format;
    }

    @Override
    public void run() {
        URL url = null;
        try {
            url = new URL(link);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            File file = new File(path + "/" + fileName);

            int sizeFile = connection.getContentLength();
            int partSize = sizeFile / numOfThread;
            int start = 0;
            int end = partSize;
            for (int i = 0; i < numOfThread - 1; i++) {
                log.info("Data of Thread Download " + (i + 1) + ": " + start + "==========>" + end);
                pool.submit(new Downloader(link, path, file, start, end));
                start = end;
                end += partSize;
            }
            end = sizeFile;
            log.info("Data of Thread Download " + numOfThread + ": " + start + "==========>" + end);
            pool.submit(new Downloader(link, path, file, start, end));
            pool.shutdown();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Main.java

package com.huantt.downloader;

import org.apache.log4j.xml.DOMConfigurator;

/**
 * Created by Huan on 7/6/2016.
 */
public class Main {
    public static void main(String[] args) {
        DOMConfigurator.configureAndWatch(".\\config\\log4j.xml");
        DownloadManager downloadManager = new DownloadManager(2,"http://pets.petsmart.com/services/_images/grooming/dog/dt_t/dog-bath-haircut.jpg","D:/");
        Thread thread = new Thread(downloadManager);
        thread.start();

        DownloadManager downloadManager1 = new DownloadManager(2,"http://pets.petsmart.com/services/_images/grooming/dog/dt_t/dog-bath-haircut.jpg","D:/","Tên Ảnh");
        Thread thread1 = new Thread(downloadManager1);
        thread1.start();
    }
}