四则运算

import java.util.Random;
import java.util.Scanner;
 
 public class si'ze'yun'suan {
     
    public static void res(){
    System.out.println("1.显示结果	2.直接开始下一题");
     }
    public static void main (String[] arge){
        int i=1;
         if(i<=30)//保证只是随机30道四则运算题目
        {
     System.out.println("*****请选择要随机生成的算法*****");
     System.out.println("1,加法	2,减法	3,乘法	4,除法");
     System.out.println("*******************************");
     Scanner sc=new Scanner(System.in);
    int s = sc.nextInt();
     double result=0;
     Random r = new Random();
     int a = r.nextInt(100);
     int b =r.nextInt(100);
     switch(s){
     case 1:System.out.println(+a+"+"+b+"=?");result =a+b;res();break;
     case 2:System.out.println(+a+"-"+b+"=?");result =a-b;res();break;
     case 3:System.out.println(+a+"*"+b+"=?");result =a*b;res();break;
     case 4:System.out.println(+a+"/"+b+"=?");{float c=a;float d=b;result=c/d;}res();break;
     default:System.out.println("输入有误，重新开始");main(null);break;
     }
     Scanner select =new Scanner(System.in);
     int se =select.nextInt();
     switch (se){
     case 1:System.out.println("本题的结果："+result);main(null);break;
     case 2:main(null);break;
    default:System.out.println("输入有误，重新开始");main(null);
     }
         i++;
     }
     }
 
     }