将多个txt合并为一个txt

import java.io.*;
public class CombineTest {
public static void main(String[] args){ 
        FileInputStream fis = null;
        FileInputStream fs = null;
        int n=258;
        byte[] b1 = new byte[1];
        byte[] b2 = new byte[1];
        try {
            java.io.File file = new java.io.File("D:\\123.txt");        
            java.io.FileOutputStream fos = new java.io.FileOutputStream(file);
            for(int i=1;i<=n;i++){
           fis = new FileInputStream(new File("D:\\4000\\苹果\\"+i+".txt"));
           String s = new String("\r\n");
           b2=s.getBytes();
           while((fis.read(b1))!=-1){
           fos.write(b1);
           }

           fos.write(b2);
           fos.write(b2);
          
           fos.flush();
            }
           System.out.println("success!");
      }
     catch(Exception e){System.out.println("error: " + e);}
   }
}