四则运算-升级版--1

import java.util.*;
import java.util.Random;
public class SiZe {

    /**
     * @param args
     */
    public static void main(String[] args) {
        
        String[] str_1 = new String[] {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9"};
        String[] str_2 = new String[] { "+", "-", "*", "/"};
        int index = 0;
        int index_1 = 0;
        int index_2 = 0;
        int[] a = new int[2];
        double data = 0;
        double answer = 0;
        System.out.println("以下有20道简单的四则运算！");
        for(int k = 0; k < 20; k++)
        {
            System.out.print("第"+(k+1)+"道题：");
            for(int i = 0; i < 2; i++)
            {
                int j = 0;
                index_1 = new Random().nextInt(9);
            
                
                if(str_2[index_2].equals("/"))
                {
                    
                    while(i >= 2 && index_1 == 0)
                    {
                        index_1 = new Random().nextInt(9);
                    }
                }
                
                a[i] = index_1;
                System.out.print(str_1[index_1]);
                if(i != 1)
                {
                    index_2 = new Random().nextInt(4);
                    System.out.print(str_2[index_2]);
                }
            }
        
            System.out.println();
            System.out.print("请输入答案：");
            Scanner input = new Scanner(System.in);
            data =input.nextDouble();
            
            switch(index_2)
            {
                case 0:
                    answer = a[0] + a[1];
                    break;
                case 1:
                    answer = a[0] - a[1];
                    break;
                case 2:
                    answer = a[0] * a[1];
                    break;
                case 3:
                    answer = (double)a[0] / a[1];
                    break;
            }
            
            if(data == answer)
                System.out.println("你输入的答案正确！");
            else
                System.out.println("你输入的答案错误！");
            
            System.out.println();
        }
    }

}