初学java实在是找不出问题所在了

Question

import java.io.*;
public class TestBufferedReader {
    public static void main(String[] args) {

        try{
            BufferedReader br = new BufferedReader(new FileReader("f:/src/io.txt"));
            BufferedWriter bw = new BufferedWriter(new FileWriter("f:/src/read2.txt"));
            String m;
            do{
                m = br.readLine();
                if(m == null ){
                    System.exit(-1);
                }
                //System.out.println(m);
                bw.write(m,0,m.length());
            } while(m != null);

            br.close();
            bw.close();
        }   
        catch(IOException e){
            e.printStackTrace();
        }


    }
}

Answer 1

我的写入文件一直为空，什么也写不进去