使用bos写的时间为0，请老师指出问题

package ioStream;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Random;

public class BufferedExercise {

    public static void main(String[] args) {
        long t1 = 0,t2=0;
        Random r=new Random();
        try {
            
            FileOutputStream fos1= new FileOutputStream("one.txt");
            FileInputStream fis1=new FileInputStream("one.txt");
            
            //基于FileOutputStream的one.txt
            long startTime1=System.currentTimeMillis();
            int n1=0;
            while(n1<100000) {
                fos1.write((char)(65+r.nextInt(26)));
                n1++;
            }
            long endTime1=System.currentTimeMillis();
            t1=endTime1-startTime1;
            fos1.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
        //基于BufferedOutputStream的two.txt
   try {
            
       FileOutputStream fos2 = new FileOutputStream("two.txt");
        BufferedOutputStream bos=new BufferedOutputStream(fos2);
        FileInputStream fis2=new FileInputStream("two.txt");
        BufferedInputStream bis=new BufferedInputStream(fis2);
            
            
            long startTime2=System.currentTimeMillis();
            int n2=0;
            while(n2<100000) {
                bos.write((char)(65+r.nextInt(26)));
                n2++;
            }
            bos.flush();
            long endTime2=System.currentTimeMillis();
            t2=endTime2-startTime2;
            bos.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
        System.out.println("one.txt不使用缓冲流来写");
        System.out.println("用时为："+t1+"ms");
        System.out.println("two.txt使用缓冲流来写");
        System.out.println("用时为："+t2+"ms");
        System.out.println("节省时间："+(t1-t2)+"ms");
    }

}