java檔案寫入怎樣換行

import java.io.*;

 

import javax.swing.JOptionPane;

 

public class test {

public static void main(String []args){

try{

FileInputStream fis=new FileInputStream("namefile.txt");

InputStreamReader dis=new InputStreamReader(fis);

BufferedReader reader=new BufferedReader(dis);

String s,str="";

while((s=reader.readLine())!=null){

str+=s;

str+="/r/n";

System.out.println(str);

}

dis.close();

FileOutputStream fos=new FileOutputStream("namefile.txt");

DataOutputStream dos=new DataOutputStream(fos);

//BufferedWriter writer=new BufferedWriter(dos);

String ss="TonHankes";

str=str+ss;

dos.writeChars(str);

dos.close();

}

catch(IOException e){

System.out.println(e);

}

}

 

}

這是一個我寫的關於檔案寫入的代碼，但不知道怎麼實現換行，"/r/n"也不奏效跪求高手解答