JAVA中HTTP的多线程下载程序

1. public?class?DownloadNetTest?{?????private?File?fileOut;??
2. ???private?URL?url;?????private?long?fileLength=0;??
3. ???//初始化线程数?????private?int?ThreadNum=5;??
4. ???public?DownloadNetTest(){?????try{??
5. ??????System.out.println("正在链接URL");????????url=new?URL("http://211.64.201.201/uploadfile/nyz.mp3");??
6. ??????HttpURLConnection?urlcon=(HttpURLConnection)url.openConnection();????????fileLength=urlcon.getContentLength();??
7. ??????if(urlcon.getResponseCode()>=400){????????System.out.println("服务器响应错误");??
8. ??????System.exit(-1);????????}??
9. ??????if(fileLength<=0)????????System.out.println("无法获知文件大小");??
10. ??????//打印信息????????printMIME(urlcon);??
11. ??????System.out.println("文件大小为"+fileLength/1024+"K");????????//获取文件名??
12. ??????String?trueurl=urlcon.getURL().toString();????????String?filename=trueurl.substring(trueurl.lastIndexOf('/')+1);??
13. ??????fileOut=new?File("D://",filename);?????}??
14. ???catch(MalformedURLException?e){????????System.err.println(e);??
15. ???}?????catch(IOException?e){??
16. ??????System.err.println(e);?????}??
17. ???init();??}??
18. ???private?void?init(){????????DownloadNetThread?[]?down=new?DownloadNetThread[ThreadNum];??
19. ???try?{????????for(int?i=0;i<ThreadNum;i++){??
20. ?????????RandomAccessFile?randOut=new?RandomAccessFile(fileOut,"rw");???????????randOut.setLength(fileLength);??
21. ?????????long?block=fileLength/ThreadNum+1;???????????randOut.seek(block*i);??
22. ?????????down[i]=new?DownloadNetThread(url,randOut,block,i+1);???????????down[i].setPriority(7);??
23. ?????????down[i].start();????????}??
24. ???//循环判断是否下载完毕?????boolean?flag=true;??
25. ???while?(flag)?{????????Thread.sleep(500);??
26. ??????flag?=?false;????????for?(int?i?=?0;?i?<?ThreadNum;?i++)??
27. ??????if?(!down[i].isFinished())?{????????flag?=?true;??
28. ??????break;????????}??
29. ??}//?end?while?????System.out.println("文件下载完毕，保存在"+fileOut.getPath()?);??
30. ???}?catch?(FileNotFoundException?e)?{???????????System.err.println(e);??
31. ?????????e.printStackTrace();?????}??
32. ???catch(IOException?e){????????System.err.println(e);??
33. ??????e.printStackTrace();?????}??
34. ???catch?(InterruptedException?e)?{?????System.err.println(e);??
35. ???}??}??
36. private?void?printMIME(HttpURLConnection?http){?????for(int?i=0;;i++){??
37. ???String?mine=http.getHeaderField(i);?????if(mine==null)??
38. ???return;?????System.out.println(http.getHeaderFieldKey(i)+":"+mine);??
39. ???}??}??
40. public?static?void?main(String[]?args)?{?????????DownloadNetTest?app=new?DownloadNetTest();??
41. }??}??

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