流与文件的四则运算

package 文件操作流;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStreamWriter;

import java.util.Random;
import java.util.Scanner;

public class SZYSfile {
 public static void main(String args[])throws IOException,ClassNotFoundException {
  
  File f = new File("D:\","Test.txt");
  f.createNewFile();
  FileOutputStream fis = new FileOutputStream(f);
  OutputStreamWriter osw = new OutputStreamWriter(fis);
  int[] answer = new int [100];//存答案
  for(int i = 0 ; i < 100;i++) {
   int a = new Random().nextInt(10);//随机数a
   int b = new Random().nextInt(10);//随机数b
   int suijifu = new Random().nextInt(4);//随机运算符
   String symbol=" ";
  switch(suijifu) {
      case(0):
           {symbol = "+";answer[i]=a+b;   break;}
      case(1):
           {symbol = "-";answer[i]=a-b;   break;}
      case(2):
           {symbol ="×";answer[i]=a*b;   break;}
      case(3):
                 if(b==0) { symbol = "+";answer[i]=a+b;   break;}
                  else
                   if(a%b!=0) {symbol = "-";answer[i]=a-b;   break;}
               else
                if(a%b==0) {symbol = "÷";answer[i]=a/b;   break;}
  } 
  osw.write(a+symbol+b+"=");
  osw.write(" ");
  }
  osw.close();
  //读取文件中的运算
  File file = new File("D:\Test.txt");
        int i=0;
       
        int score = 0;
        if(file.exists()){ 
            try { 
                FileReader fileReader = new FileReader(file); 
                BufferedReader br = new BufferedReader(fileReader); 
                String lineContent = null; 
                while((lineContent = br.readLine())!=null){ 
                    System.out.println(lineContent);
                  
                    Scanner input = new Scanner(System.in);
                    int a=input.nextInt();
                   
                    if(a==answer[i]) {
                     System.out.println("回答正确！");
                     score++;
                    }
                    else
                     {System.out.println("回答错误! 答案是"+answer[i]);}
                    
                    i++;
                } 
                br.close(); 
                fileReader.close(); 
               
            } catch (FileNotFoundException e1) { 
                System.out.println("no this file");//文件不存在抛异常 
                e1.printStackTrace(); 
            } catch (IOException e1) { 
                System.out.println("io exception"); 
                e1.printStackTrace();
               
            }
        } System.out.println("分数为："+score);
   
    }
}