Java-->多线程断点续传

--> 在多线程复制的基础上加入断点续传的功能

-->Test 测试类

package com.dragon.java.multithreaddownload;

import java.io.File;

/*
 * 多线程断点续传（下载）
 */
public class Test {
    public static void main(String[] args) {
        // @SuppressWarnings("resource")
        // Scanner scanner = new Scanner(System.in);
        // System.out.println("请输入文件路径：");
                // 直接写死文件和线程数..
        File srcFile = new File("F:/mp4/01_Java.mp4");
        // System.out.println("请输入线程数：");
        // int n = scanner.nextInt();
        int n = 4;
        if (!srcFile.exists()) {
            System.out.println("该文件不存在！");
        }

        File desFile = new File(srcFile.getParent(), "new" + srcFile.getName());

                // 单线程复制长度
        long partLenghth = srcFile.length() / n + 1;
        for (int i = 1; i < n + 1; i++) {
                        // 启动线程
            new MyThread(srcFile, desFile, partLenghth * (i - 1), partLenghth
                    * i).start();

        }
    }
}

--> MyThread 线程实现类

package com.dragon.java.multithreaddownload;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

public class MyThread extends Thread {
    private File srcFile;
    private File desFile;
    private long start;
    private long end;

    MyThread() {
        super();
    }

    MyThread(File srcFile, File desFile, long start, long end) {
        super();
        this.srcFile = srcFile;
        this.desFile = desFile;
        this.start = start;
        this.end = end;
    }

    @Override
    public void run() {
                // 创建配置文件存储中断时的文件指针
        File configFile = new File(desFile.getParent(), Thread.currentThread()
                .getId() + ".config");
        if (!configFile.exists() && desFile.exists()) {
        
System.out.println(Thread.currentThread().getName() + "已经完成了下载");
            return;
        }
                // 将流写在try() 中可以不需手动关闭流
        try (RandomAccessFile rafSrc = new RandomAccessFile(srcFile, "r");
                RandomAccessFile rafDes = new RandomAccessFile(desFile, "rw");
                RandomAccessFile rafConfig = new RandomAccessFile(configFile,
                        "rw");) {

            rafConfig.setLength(8);

                        // 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
            long pointer = rafConfig.readLong();
            if (pointer != 0) {
                start = pointer;
            }
            rafSrc.seek(start);
            rafDes.seek(start);

// 显示完成度 System.out.println(Thread.currentThread().getName() + "已下载："
                    + ((float) pointer / srcFile.length()) * 100 + "%");

            int len = -1;
            byte[] buffer = new byte[32];
            while ((len = rafSrc.read(buffer)) != -1) {
                rafDes.write(buffer, 0, len);
                pointer = rafSrc.getFilePointer();
                rafConfig.seek(0);
                rafConfig.writeLong(pointer);
                                // 当每个线程完成任务时结束线程
                if (rafSrc.getFilePointer() >= end) {
                    break;
                }
            }
        } catch (IOException e) {
            System.out.println(e);
        }
                // 删除配置文件
        configFile.delete();
    }
}