JAVA的HTTP多线程下载程序

JAVA的HTTP多线程下载程序。自己教学中使用的一段程序。

java 代码

 

1. public class DownloadNetTest {
2. private File fileOut;
3. private URL url;
4. private long fileLength=0;
5. //初始化线程数
6. private int ThreadNum=5;
7. public DownloadNetTest(){
8. try{
9. System.out.println("正在链接URL");
10. url=new URL("http://211.64.201.201/uploadfile/nyz.mp3");
11. HttpURLConnection urlcon=(HttpURLConnection)url.openConnection();
12. fileLength=urlcon.getContentLength();
13. if(urlcon.getResponseCode()>=400){
14. System.out.println("服务器响应错误");
15. System.exit(-1);
16. }
17. if(fileLength<=0)
18. System.out.println("无法获知文件大小");
19. //打印信息
20. printMIME(urlcon);
21. System.out.println("文件大小为"+fileLength/1024+"K");
22. //获取文件名
23. String trueurl=urlcon.getURL().toString();
24. String filename=trueurl.substring(trueurl.lastIndexOf('/')+1);
25. fileOut=new File("D://",filename);
26. }
27. catch(MalformedURLException e){
28. System.err.println(e);
29. }
30. catch(IOException e){
31. System.err.println(e);
32. }
33. init();
34. }
35. private void init(){
36. DownloadNetThread [] down=new DownloadNetThread[ThreadNum];
37. try {
38. for(int i=0;i<ThreadNum;i++){
39. RandomAccessFile randOut=new RandomAccessFile(fileOut,"rw");
40. randOut.setLength(fileLength);
41. long block=fileLength/ThreadNum+1;
42. randOut.seek(block*i);
43. down[i]=new DownloadNetThread(url,randOut,block,i+1);
44. down[i].setPriority(7);
45. down[i].start();
46. }
47. //循环判断是否下载完毕
48. boolean flag=true;
49. while (flag) {
50. Thread.sleep(500);
51. flag = false;
52. for (int i = 0; i < ThreadNum; i++)
53. if (!down[i].isFinished()) {
54. flag = true;
55. break;
56. }
57. }// end while
58. System.out.println("文件下载完毕，保存在"+fileOut.getPath() );
59. } catch (FileNotFoundException e) {
60. System.err.println(e);
61. e.printStackTrace();
62. }
63. catch(IOException e){
64. System.err.println(e);
65. e.printStackTrace();
66. }
67. catch (InterruptedException e) {
68. System.err.println(e);
69. }
70. }
71. private void printMIME(HttpURLConnection http){
72. for(int i=0;;i++){
73. String mine=http.getHeaderField(i);
74. if(mine==null)
75. return;
76. System.out.println(http.getHeaderFieldKey(i)+":"+mine);
77. }
78. }
79. public static void main(String[] args) {
80. DownloadNetTest app=new DownloadNetTest();
81. }
82. }