Java-->多线程断点续传

 1 package com.dragon.java.multithreaddownload;
 2 
 3 import java.io.File;
 4 
 5 /*
 6  * 多线程断点续传（下载）
 7  */
 8 public class Test {
 9     public static void main(String[] args) {
10         // @SuppressWarnings("resource")
11         // Scanner scanner = new Scanner(System.in);
12         // System.out.println("请输入文件路径：");
13                 // 直接写死文件和线程数..
14         File srcFile = new File("F:/mp4/01_Java.mp4");
15         // System.out.println("请输入线程数：");
16         // int n = scanner.nextInt();
17         int n = 4;
18         if (!srcFile.exists()) {
19             System.out.println("该文件不存在！");
20         }
21 
22         File desFile = new File(srcFile.getParent(), "new" + srcFile.getName());
23 
24                 // 单线程复制长度
25         long partLenghth = srcFile.length() / n + 1;
26         for (int i = 1; i < n + 1; i++) {
27                         // 启动线程
28             new MyThread(srcFile, desFile, partLenghth * (i - 1), partLenghth
29                     * i).start();
30 
31         }
32     }
33 }

 1 package com.dragon.java.multithreaddownload;
 2 
 3 import java.io.File;
 4 import java.io.IOException;
 5 import java.io.RandomAccessFile;
 6 
 7 public class MyThread extends Thread {
 8     private File srcFile;
 9     private File desFile;
10     private long start;
11     private long end;
12 
13     MyThread() {
14         super();
15     }
16 
17     MyThread(File srcFile, File desFile, long start, long end) {
18         super();
19         this.srcFile = srcFile;
20         this.desFile = desFile;
21         this.start = start;
22         this.end = end;
23     }
24 
25     @Override
26     public void run() {
27                 // 创建配置文件存储中断时的文件指针
28         File configFile = new File(desFile.getParent(), Thread.currentThread()
29                 .getId() + ".config");
30         if (!configFile.exists() && desFile.exists()) {
31         
32 System.out.println(Thread.currentThread().getName() + "已经完成了下载");
33             return;
34         }
35                 // 将流写在try() 中可以不需手动关闭流
36         try (RandomAccessFile rafSrc = new RandomAccessFile(srcFile, "r");
37                 RandomAccessFile rafDes = new RandomAccessFile(desFile, "rw");
38                 RandomAccessFile rafConfig = new RandomAccessFile(configFile,
39                         "rw");) {
40 
41             rafConfig.setLength(8);
42 
43                         // 当不是第一次下载时，将配置文件中的指针传递给开始指针
44             long pointer = rafConfig.readLong();
45             if (pointer != 0) {
46                 start = pointer;
47             }
48             rafSrc.seek(start);
49             rafDes.seek(start);
50 
51 // 显示完成度 System.out.println(Thread.currentThread().getName() + "已下载："
52                     + ((float) pointer / srcFile.length()) * 100 + "%");
53 
54             int len = -1;
55             byte[] buffer = new byte[32];
56             while ((len = rafSrc.read(buffer)) != -1) {
57                 rafDes.write(buffer, 0, len);
58                 pointer = rafSrc.getFilePointer();
59                 rafConfig.seek(0);
60                 rafConfig.writeLong(pointer);
61                                 // 当每个线程完成任务时结束线程
62                 if (rafSrc.getFilePointer() >= end) {
63                     break;
64                 }
65             }
66         } catch (IOException e) {
67             System.out.println(e);
68         }
69                 // 删除配置文件
70         configFile.delete();
71     }
72 }