1 package cn.test.DownLoad;  2   3 import java.io.File;  4 import java.io.InputStream;  5 import java.io.RandomAccessFile;  6 import java.net.HttpURLConnection;  7 import java.net.URL;  8   9 public class MultiPart { 10     public void down() throws Exception 11     { 12         //1、声明URL 13         String fileName="a.rar"; 14         String path="http://localhost:8080/day23_MultiThreadDownLoad/file/"+fileName; 15         URL url=new URL(path); 16         //2、返回连接对象 17         HttpURLConnection conn=(HttpURLConnection) url.openConnection(); 18         //3、设置请求类型 19         conn.setRequestMethod("GET"); 20         //4、设置允许接收消息 21         conn.setDoInput(true); 22         //5、连接 23         conn.connect(); 24         //6、状态码 25         int code=conn.getResponseCode(); 26         if(code==200) 27         { 28             int sum=conn.getContentLength();//总长度 29             String downFile="d:\\"+fileName; 30             //7、创建一个相同大小的空文件 31             RandomAccessFile file=new RandomAccessFile(new File(downFile), "rw"); 32             file.setLength(sum); 33             file.close(); 34             //8、声明线程数量 35             int threadCount=3; 36             //9、声明每个线程的下载量 37             int threadSize=sum/threadCount+((sum%threadCount==0)?0:1); 38             for(int i=0;i