java 多线程分段下载

java 多线程分段下载

介绍

使用java 多线程下载，当前只是一个demo,还没进行对比测试，目前看速度确实要快一些

实现和简单就是启用多个现成分段下载，最后再组合在一起

完整代码

原本是下载tomcat10的，但是我本地jdk不符，最后下载的8

import lombok.SneakyThrows;

import java.io.*;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class AllDown {
   // static String downUrl = "https://dlcdn.apache.org/tomcat/tomcat-10/v10.1.19/src/apache-tomcat-10.1.19-src.zip";
    static String downUrl = "https://dlcdn.apache.org/tomcat/tomcat-8/v8.5.99/bin/apache-tomcat-8.5.99-windows-x64.zip";
    public static void main(String[] args) throws IOException {
        long t1 = System.currentTimeMillis();
        URL url = new URL(downUrl);
        URLConnection conn = url.openConnection();
        conn.setRequestProperty("Accept-Encoding", "identity");
        long size =  conn.getContentLengthLong();
        System.out.println("大小" + size);
        Map<Integer, byte[]> map = new HashMap<>();
        long start = -1;
        long end = -1;
        int index = 0;
        List<Thread> list = new ArrayList<>();
        while (end < size) {
            start = end;
            end += 1000000;
            if (end >= size) {
                end = size;
            }
            System.out.println("start" + start + "," + "end" + end);
            list.add(new Thread(new Run(start+1,end,index,map)));
            index++;
        }
        list.forEach(e->e.start());
        list.forEach(e-> {
            try {
                e.join();
            } catch (InterruptedException interruptedException) {
                interruptedException.printStackTrace();
            }
        });

        System.out.println("map " + map);
        OutputStream out = new FileOutputStream("tomcat.zip");
        for(int i=0;i<map.size();i++){
            out.write(map.get(i));
        }
        out.flush();
        out.close();
        long t2 = System.currentTimeMillis();
        System.out.println("耗费时间" + (t2-t1) + "ms");

    }

}

class Run implements Runnable {

    long start;
    long end;
    Integer index;
    Map<Integer, byte[]> map;

    public Run(long start,
               long end,
               Integer index,
               Map<Integer, byte[]> map) {
        this.start = start;
        this.end = end;
        this.index = index;
        this.map = map;

    }

    @SneakyThrows
    @Override
    public void run() {
        URL url = new URL(AllDown.downUrl);
        URLConnection conn = url.openConnection();
        conn.setRequestProperty("Range", "bytes=" + start + "-" + end);
        InputStream in = conn.getInputStream();
        int len = -1;
        byte[] buff = new byte[2048];
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        while ((len = in.read(buff)) > -1) {
            out.write(buff,0,len);
        }
        out.flush();
        map.put(index, out.toByteArray());
        out.close();
        in.close();
    }
}

日志

大小12482200
start-1,end999999
start999999,end1999999
start1999999,end2999999
start2999999,end3999999
start3999999,end4999999
start4999999,end5999999
start5999999,end6999999
start6999999,end7999999
start7999999,end8999999
start8999999,end9999999
start9999999,end10999999
start10999999,end11999999
start11999999,end12482200
map {0=[B@7e9131d5, 1=[B@2e1d27ba, 2=[B@61d6015a, 3=[B@2525ff7e, 4=[B@524d6d96, 5=[B@152aa092, 6=[B@44a7bfbc, 7=[B@4ef37659, 8=[B@776b83cc, 9=[B@37858383, 10=[B@4e268090, 11=[B@1bb266b3, 12=[B@306cf3ea}
耗费时间33111ms

本地浏览器下载

还是有一些提升的

最后

解压打开后