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@Overridepublic 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