四则运算

package size;
import java.io.PrintWriter;
import java.util.Scanner;
import java.io.FileNotFoundException;
class Counter
{
private int a,b;

 public int  add(int a,int b) 
 { 
     return a+b; 
 } 
 public int   reduce(int a,int b) 
 { 
     return a-b; 
 } 
 public int   multiplication(int a,int b) 
 { 
     return a*b; 
 } 
 public int   division(int a,int b) 
 { 
     if(b!=0) 
     return a/b; 
     else return 0; 
 } 

}
public class size {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
Counter counter=new Counter();
PrintWriter out = null;
try {
out = new PrintWriter("text.txt");
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
int sum = 0;

    for (int i = 1; i <=10; i++) { 
        int a = (int) Math.round(Math.random() * 100); 
        int b = (int) Math.round(Math.random() * 100); 
        int t= (int) Math.round(Math.random() * 1); 
        
       switch(t) 
       { 
       case 0: 
           System.out.println(i+": "+a+"/"+b+"="); 
           
           while(b==0){  b = (int) Math.round(Math.random() * 100); } 
           
        int c0 = in.nextInt(); 
        out.println(a+"/"+b+"="+c0); 
        if (c0 == counter.division(a, b)) { 
            sum += 10; 
            System.out.println("恭喜答案正确"); 
        } 
        else { 
            System.out.println("答案错误"); 
        } 
        
        break; 
        
       case 1: 
           System.out.println(i+": "+a+"*"+b+"="); 
           int c = in.nextInt(); 
           out.println(a+"*"+b+"="+c); 
           if (c == counter.multiplication(a, b)) { 
               sum += 10; 
               System.out.println("恭喜答案正确"); 
           } 
           else { 
               System.out.println("答案错误"); 
           } 
           break; 
       case 2: 
           System.out.println(i+": "+a+"+"+b+"="); 
           int c1 = in.nextInt(); 
           out.println(a+"+"+b+"="+c1); 
           if (c1 == counter.add(a, b)) { 
               sum += 10; 
               System.out.println("恭喜答案正确"); 
           } 
           else { 
               System.out.println("答案错误"); 
           } 
           
           break ; 
       case 3: 
           System.out.println(i+": "+a+"-"+b+"="); 
           int c2 = in.nextInt(); 
           out.println(a+"-"+b+"="+c2); 
           if (c2 == counter.reduce(a, b)) { 
               sum += 10; 
               System.out.println("恭喜答案正确"); 
           } 
           else { 
               System.out.println("答案错误"); 
           } 


         break ; 
           } 

      } 
    System.out.println("成绩"+sum); 
    out.println("成绩:"+sum); 
     out.close();       
} 

}