多线程，复制文件没有成功

package edu.uestc.avatar.demo;

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

public class FileCopy {

    public static void main(String[] args) {

        Thread thread1 = new Thread(new Copy());

        thread1.start();

        System.out.println("复制完成");
    }

}

class Copy implements Runnable {

    @Override
    public void run() {
        File srcFile = new File("e:" + File.separator + "car.txt");// 待复制的文件 separator分离器
        File destFile = new File("e:" + File.separator + "fruit.txt");// copy的文件
        try (RandomAccessFile rf = new RandomAccessFile(srcFile, "r");
                RandomAccessFile wf = new RandomAccessFile(destFile, "rw")) {
            byte[] buff = new byte[1024];
            int len = -1;
            while ((len = rf.read()) != -1) {
                wf.write(buff, 0, len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

复制不上，不太清楚为什么

找到问题了，rf.read里面放buff数据就行了。细节问题。