四则运算缓冲流

package sizeyuansuan;
import java.io.*;
import java.util.*;
public class Sizeyuansuan {
    public static void main(String[] args)throws IOException
    {
        FileOutputStream outfile= new FileOutputStream(new File("sizeyuansuan.txt"));
        PrintStream printStream= new PrintStream(outfile);
        FileInputStream infile= new FileInputStream("sizeyuansuan.txt");
        InputStreamReader reader = new InputStreamReader(infile, "UTF-8");
         StringBuffer buffer = new StringBuffer();
        Scanner in=new Scanner(System.in);
        int a=0;
        int b=0;
        int sum;
        int count=0;
        double[] num=new double[100];
        int i;
        for(i=0;i<100;i++)
        {
            a= (int)(Math.random()*10+1);
            b=(int)(Math.random()*10+1);
            int number=(int)(Math.random()*30);
            if(number%4==0)
            {
                sum=a+b;
                printStream.print(a);
                printStream.print("+");
                printStream.print(b);
                printStream.print("=");
                printStream.print(sum);
                printStream.append("
");
                num[i]=sum;
            }
            if(number%4==1)
            {
                sum=a-b;
                printStream.print(a);
                printStream.print("-");
                printStream.print(b);
                printStream.print("=");
                printStream.print(sum);
                printStream.append("
");
                num[i]=sum;
            }
            if(number%4==2)
            {
                sum=a*b;
                printStream.print(a);
                printStream.print("*");
                printStream.print(b);
                printStream.print("=");
                printStream.print(sum);
                printStream.append("
");
              num[i]=sum;
            }
            if(number%4==3)
            {
                sum=a/b;
                printStream.print(a);
                printStream.print("/");
                printStream.print(b);
                printStream.print("=");
                printStream.print(sum);
                printStream.append("
");
                num[i]=sum;
            }
        }
        printStream.close();
        int test;
        double Sum;
        for(i=0;i<100;i++)
        {
        while ((test= reader.read()) != '=')
        {
            System.out.print((char)test);
        }
        Sum=in.nextDouble();
        if(Sum==num[i])
        {
            System.out.println("ture");
            count++;
        }
        else
        {
            System.out.println("false");
        }
        }
        System.out.println("ture:"+count+"   false:"+(100-count));
        reader.close();
    }
}

遇到的困难：1.报错thread "main" java.lang.ArithmeticException: 意思为：运算异常，后我改正了随机数的生成，修改了错误。

                      2.不会缓冲流文本输入，后在网络上学习，学会了缓冲流的输入。

                      3.长数组赋初值初始化麻烦，后采用这种方法初始化double[] num=new double[100];

              备注：除法答案对比无法完成，因为除法答案的小数位除不尽时无法判断。

完成时间：  20:00