本地文件多线程复制

class Copy extends Thread{
    RandomAccessFile tager;
    RandomAccessFile copy;
    long downSize;

    /**
     * 
     * @param path  靶文件路径
     * @param copy  复制后的文件路径
     * @param downTotal 下载的子线程总数
     * @param downNumber    当前的子线程编号
     */
    public Copy(String path,String copy,int downTotal,int downNumber){
        try {
            File f1=new File(path);
            File f2=new File(copy);
            tager=new RandomAccessFile(f1,"r");
            this.copy=new RandomAccessFile(f2, "rw");
            downSize=f1.length()/downTotal==0?f1.length()/downTotal:(f1.length()/downTotal)+1;
            tager.seek(downSize*downNumber);
            this.copy.seek(downSize*downNumber);

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public void run(){
        byte[] buf=new byte[1024];
        int len=0;
        long sum=0;
        try {
            while((len=tager.read(buf))!=-1&&sum<downSize){
                copy.write(buf,0,len);
                sum+=len;
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}