1 public static int calculate(String ss) {
 2         int res = 0, save = 0, n = 0;
 3         char s[] = ss.toCharArray();
 4         char sign = '+';//初始符号为+
 5         for (int i = 0; i < s.length; ++i) {
 6             if (s[i] >= '0') {
 7                 n = n * 10 + s[i] - '0';//读入两位数或一位数
 8                 if (i == s.length - 1 || s[i + 1] < '0') {
 9
10                     if (sign == '+') {
11                         if (res < 0)//此类判断标记了负数情况
12                             ok = false;
13                         res += n;
14                         save = n;
15                     } else if (sign == '-') {
16                         if (res < 0)
17                             ok = false;
18                         res -= n;
19                         save = -1 * n;
20                     } else if (sign == '*') {
21                         res = res - save + save * n;
22                         if (res < 0)
23                             ok = false;
24                         save = save * n;
25                     } else if (sign == '/') {
26                         res = res - save + save / n;
27                         if (res < 0)
28                             ok = false;
29                         save = save / n;
30                     }
31                 }
32             } else {
33                 n = 0;
34                 sign = s[i];
35             }
36         }
37         return res;
38     }

 1 if (operas[i] == '/') {// 除法处理为大数除以两数最大公约数
 2             if (nums[i + 1] == 0)
 3                 nums[i + 1] = 2;// 避免除数为零
 4             if (nums[i] < nums[i + 1]) {
 5                 int t = nums[i];
 6                 nums[i] = nums[i + 1];
 7                 nums[i + 1] = t;
 8             }
 9             nums[i + 1] = gcd(nums[i], nums[i + 1]);
10             if (nums[i + 1] == 1) {
11                 ok = false;
12             }
13         }