怎么用Java实现将500万条行记录分别均匀拆分到多个磁盘上

参考以下代码：

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.text.DecimalFormat;
import java.util.Random;

public class Test {

public static void main(String[] args) throws Exception {

File src = new File("D:\\src.txt");
File dest = new File("D:\\dest");
FileReader fr = new FileReader(src);
BufferedReader br = new BufferedReader(fr);
int lineno = 1;
int index = 1;
dest.mkdirs();
FileWriter fw = new FileWriter(new File(dest, creIndex(index++)

".txt"));
(br.ready()) {
(lineno++ % 500 == 0) {
fw.close();
= new FileWriter(new File(dest, creIndex(index++) + ".txt"));
}
String line = br.readLine();
fw.write(line + "\r\n");
}
fw.close();
br.close();
fr.close();
}
public static String creIndex(int num) {
DecimalFormat df = new DecimalFormat("00");
return df.format(num);
}
}