1 package demo;
 2 
 3 import java.text.DecimalFormat;
 4 import java.util.Random;
 5 
 6 public class Demo {
 7 
 8     public static void main(String[] args) {
 9         maths();
10     }
11 
12     public static void maths() {
13         Random number = new Random();
14         for (int x = 1; x <= 300; x++) {
15             int compute = number.nextInt(4);
16             int a = number.nextInt(100);
17             int b = number.nextInt(100);
18             switch (compute) {
19             case 0:
20                 System.out.println("第" + x + "条：");
21                 System.out.println(a + "+" + b + "=" + (a + b));
22                 break;
23             case 1:
24                 System.out.println("第" + x + "条：");
25                 System.out.println(a + "-" + b + "=" + (a - b));
26                 break;
27             case 2:
28                 System.out.println("第" + x + "条：");
29                 System.out.println(a + "×" + b + "=" + (a * b));
30                 break;
31             case 3:
32                 if (b == 0) {
33                     x--;
34                     break;
35                 } else {
36                     if (a % b == 0) {
37                         System.out.println("第" + x + "条：");
38                         System.out.println(a + "÷" + b + "=" + (a / b));
39                     } else {
40                         System.out.println("第" + x + "个:");
41                         double c = (double) a / b;
42                         String y = new DecimalFormat("0.00").format(c);
43                         System.out.println(a + "÷" + b + "=" + y);
44                     }
45                 }
46                 break;
47             default:
48                 break;
49             }
50         }
51     }
52 }