實現多線程拷貝一個文件

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.text.DecimalFormat;
import java.util.Date;

class FileCopy implements Runnable{
    private File src;//源文件
    private File tar;//目標文件
    private int n;//分幾部分
    private int no;//每部分的編號
    Date startDate = new Date();
    public FileCopy(File src, File tar, int n, int no) {
        this.src = src;
        this.tar = tar;
        this.n = n;
        this.no = no;
    }

    @Override
    public void run() {
        try {
            RandomAccessFile rafsrc = new RandomAccessFile(src,"r");
            String fileName = src.getName();
            tar = new File(tar + File.separator + fileName);
            RandomAccessFile raftar = new RandomAccessFile(tar,"rw");
            long len = src.length();
            long size = len % n == 0 ? len / n : len / n + 1;//每部分的字節數
            byte[] b = new byte[1024 * 8];//每次讀取的文件大小
            int num = 0;//每次讀取的字節數
            long start = size * no;//讀寫的起始位置
            rafsrc.seek(start);
            raftar.seek(start);
            double sum = 0;//累加每次讀取個數
            DecimalFormat df = new DecimalFormat("##.00%");
            while((num = rafsrc.read(b)) != -1 && sum < size){
                raftar.write(b, 0, num);
                sum += num;
                double d = sum / len;
                System.out.println(fileName + "已復制的進度：" + df.format(d));
            }
            System.out.println(src.getName() + "復制完成！");
            System.out.println("復制文件用" + n + "線程，用時：" + (new Date().getTime()-startDate.getTime()));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e1){
            e1.printStackTrace();
        }
    }
}
/**
 * @Description:ლ【多線程】ლ->復制文件
 * @Param:
 * @Return:
 * @Author: Mr.li
 * @Date: 2020/1/3
 */
public class TestFileCopy {
    public static void main(String[] args){
        File src = new File("/Users/lzl/Desktop/personal_word/a/img_tx.zip");
        File tar = new File("/Users/lzl/Desktop/personal_word/b");
        int n = 5;
        //分幾部分復制
        for(int i = 0;i < n; i++){//每一部分的編號
            new Thread(new FileCopy(src, tar, n, i)).start();
        }

    }
}