1 import java.io.IOException; 2 import java.io.InputStream; 3 import java.io.RandomAccessFile; 4 import java.net.HttpURLConnection; 5 import java.net.MalformedURLException; 6 import java.net.ProtocolException; 7 import java.net.URL; 8  9 /**10  * 线程类11  * @author Administrator12  *13  */14 public class DownThread extends Thread{15     16     private String path;17     private int startPos;18     private int currentPartSize;19     private RandomAccessFile currentPart;20     21     public int length;22     23     public DownThread(String path, int startPos, int currentPartSize,24             RandomAccessFile currentPart) {25         26         this.path = path;27         this.startPos = startPos;28         this.currentPartSize = currentPartSize;29         this.currentPart = currentPart;30     }31 32     @Override33     public void run() {34         try {35             URL url = new URL(path);36             HttpURLConnection conn;37             conn = (HttpURLConnection)url.openConnection();38             /* 设置超时时长 */39             conn.setConnectTimeout(5000);40             /* 设置发送请求的方法 */41             conn.setRequestMethod("GET");42             43             conn.setRequestProperty("Accept", "image/gif, image/x-xbitmap, " +44                     "image/jpeg, image/pjpeg, application/x-shockwave-flash, " +45                     "application/vnd.ms-excel, application/vnd.ms-powerpoint, " +46                     "application/msword, application/x-silverlight, */*");47             48             conn.setRequestProperty("Accept-Language", "zh-CN");49             conn.setRequestProperty("Charset", "UTF-8");50             /* 返回该Socket对象对应的输出流，让程序通过该输入流从Socket中取出数据 */51             InputStream inStream = conn.getInputStream();52             inStream.skip(startPos);//寻到开始下载的位置53             byte[] buffer = new byte[1024];54             int hasRead = 0;55             while(length < currentPartSize && (hasRead = inStream.read(buffer)) > 0){56                 currentPart.write(buffer, 0, hasRead);57                 length += hasRead;58             }59             currentPart.close();60             inStream.close();61         } catch (MalformedURLException e) {62             e.printStackTrace();63         } catch (ProtocolException e) {64             e.printStackTrace();65         } catch (IOException e) {66             e.printStackTrace();67         }68     }69     70     71 }

 1 import java.io.RandomAccessFile; 2 import java.net.HttpURLConnection; 3 import java.net.URL; 4  5  6 public class DownUtil { 7     /* 下载资源的路径--url */ 8     private String path; 9     private String targetFile;10     private int threadNum;11     /* 多线程下载 */12     private DownThread[] threads;13     private int fileSize;14     public DownUtil(String path, String targetFile, int threadNum) {15         16         this.path = path;17         this.targetFile = targetFile;18         threads = new DownThread[threadNum];19         this.threadNum = threadNum;20     }21     22     public void download() throws Exception{23         URL url = new URL(path);24         HttpURLConnection conn;25         conn = (HttpURLConnection)url.openConnection();26     27         conn.setConnectTimeout(5000);28         29         conn.setRequestMethod("GET");30         31         conn.setRequestProperty("Accept", "image/gif, image/x-xbitmap, " +32                 "image/jpeg, image/pjpeg, application/x-shockwave-flash, " +33                 "application/vnd.ms-excel, application/vnd.ms-powerpoint, " +34                 "application/msword, application/x-silverlight, */*");35         36         conn.setRequestProperty("Accept-Language", "zh-CN");37         conn.setRequestProperty("Charset", "UTF-8");38         conn.setRequestProperty("Connection", "Keep-Alive");39         /* 得到文件的大小 */40         fileSize = conn.getContentLength();41         conn.disconnect();42         int currentPartSize = fileSize / threadNum + 1;43         RandomAccessFile file = new RandomAccessFile(targetFile, "rw");44         /* 设置本地文件的大小 */45         file.setLength(fileSize);46         file.close();47         48         for (int i = 0; i < threadNum; i++) {49             int startPos = i * currentPartSize;50             /* 每个线程使用一个RandomAccessFile进行下载 */51             RandomAccessFile currentPart = new RandomAccessFile(targetFile, "rw");52             /* 定位文件下载的位置*/53             currentPart.seek(startPos);54             threads[i] = new DownThread(path, startPos, currentPartSize, currentPart);55             threads[i].start();56         }57     }58     59     public double getCompleteRate(){60         int sumSize = 0;61         for (int i = 0; i < threadNum; i++) {62             sumSize += threads[i].length;63         }64         return sumSize * 1.0 / fileSize;65     }66 }