问题描述：

对于任意字符串，包含+ - * /和括号， 求出该表达式的值

首先百度该问题，网上有不少答案，但是实际思考，发现，很多答案没有考虑完全，例如：

-1+（-2）*3       遇到负号怎么办？

现贴出代码如下：

  1 package calcultor;
  2 
  3 import java.util.Stack;
  4 
  5 public class Calcultor {
  6 
  7     static boolean isNumber(char x) {
  8         if (x >= '0' && x <= '9') {
  9             return true;
 10         }
 11         return false;
 12     }
 13 
 14     static int priority(char x) {
 15         if (x == '+' || x == '-') {
 16             return 0;
 17         } else if (x == '*' || x == '/') {
 18             return 1;
 19         } else if (x == '(' || x == ')') {
 20             return -1;
 21         } else if (x == '#') {
 22             return -2;
 23         }
 24 
 25         return -3;
 26     }
 27 
 28     public static int calculte(String s) {
 29         Stack<Integer> number = new Stack<Integer>();
 30         Stack<Character> operate = new Stack<Character>();
 31         char top;
 32         int a = 0, b = 0;
 33         int j = 0;
 34         boolean flag = false;
 35         for (int i = 0; i < s.length(); ++i) {
 36             if (s.charAt(1) == '-') {
 37                 flag = true;
 38             }
 39             if (i >= 2 && i <= s.length() - 2) {
 40                 j = i;
 41                 if (!isNumber(s.charAt(j - 1)) && s.charAt(i) == '-' && isNumber(s.charAt(j + 1))) {
 42                     flag = true;
 43                 }
 44             }
 45             if (isNumber(s.charAt(i))) {
 46                 int Temp = 0;
 47                 String temp = "";
 48                 temp += s.charAt(i);
 49                 while (isNumber(s.charAt(++i)))
 50                     temp += s.charAt(i);
 51                 for (int jj = 0; jj < temp.length(); ++jj) {
 52                     Temp = Temp * 10 + temp.charAt(jj) - 48;
 53                 }
 54                 if (flag) {
 55                     Temp *= -1;
 56                     flag = !flag;
 57                 }
 58                 number.push(Temp);
 59                 temp = null;
 60             }
 61             if (!isNumber(s.charAt(i))) {
 62                 if (((s.charAt(i) == '-') && !flag) || (s.charAt(i) != '-')) {
 63                     if (operate.empty()) {
 64                         operate.push(s.charAt(i));
 65                     } else {
 66                         top = operate.peek();
 67                         if (priority(s.charAt(i)) > priority(top) || s.charAt(i) == '(') {
 68                             operate.push(s.charAt(i));
 69                         } else {
 70                             while (priority(s.charAt(i)) <= priority(top)) {
 71                                 if (top == '#' && s.charAt(i) == '#') {
 72                                     int answer;
 73                                     operate.pop();
 74                                     answer = number.peek();
 75                                     number.pop();
 76                                     return answer;
 77                                 } else if (top == '(' && s.charAt(i) == ')') {
 78                                     ++i;
 79                                 } else {
 80                                     a = number.peek();
 81                                     number.pop();
 82                                     b = number.peek();
 83                                     number.pop();
 84                                 }
 85                                 if (top == '+') {
 86                                     b += a;
 87                                     number.push(b);
 88                                 } else if (top == '-') {
 89                                     b -= a;
 90                                     number.push(b);
 91                                 } else if (top == '*') {
 92                                     b *= a;
 93                                     number.push(b);
 94                                 } else if (top == '/') {
 95                                     b /= a;
 96                                     number.push(b);
 97                                 }
 98                                 operate.pop();
 99                                 top = operate.peek();
100                             }
101                             operate.push(s.charAt(i));
102                         }
103                     }
104                 }
105             }
106         }
107 
108         return 0;
109     }
110 
111     public static void main(String[] args) {
112         String s = new String("#(1+2)+6/3+(-2*2)+(-2*6)#");
113         int answer = calculte(s);
114         System.out.println("the answer is " + answer);
115     }
116 }