无括号简单四则运算器

转载请注明作者与出处：francsico http://www.cnblogs.com/franciscolv/archive/2011/11/20/2255860.html.

package SortSet;

import java.util.Stack;

public class OperationTest {

    private static Stack<Character> opeStack = new Stack<Character>();
    private static Stack<Integer> numStack = new Stack<Integer>();

    private static StringBuilder in = new StringBuilder();
    private static StringBuilder number = new StringBuilder();

    public static void main(String[] args) {
        System.out.println(cal("4+6*8-5+2*11"));
    }

    public static int cal(String input) {
        in.append(input);
        while (in.length() > 0) {
            char temp = in.charAt(0);
            in.delete(0, 1);
            if (temp > '0' && temp < '9') {
                number.append(temp);    
            } else {
                if (!"".equals(number.toString())) {
                    int num = Integer.parseInt(number.toString());
                    numStack.push(num);
                    number.delete(0, number.length());
                }
                while (!opeStack.isEmpty() && !compare(temp)) {
                    int num2 = numStack.pop();
                    int num1 = numStack.pop();
                    char ope = opeStack.pop();
                    cal0(ope,num1,num2);
                }
//                if (temp != '#' && compare(temp)) {
                    opeStack.push(temp);
//                }
            }
        }
        if(number.length()>0){
            int num = Integer.parseInt(number.toString());
            numStack.push(num);
        }
        while(!opeStack.isEmpty()){
            int num2= numStack.pop();
            int num1= numStack.pop();
            cal0(opeStack.pop(),num1,num2); 
        }
            
        return numStack.pop();
    }

    public static void cal0(char ope,int num1 ,int num2){
        switch (ope) {
        case '+':
            numStack.push(num1 + num2);
            break;
        case '-':
            numStack.push(num1 - num2);
            break;
        case '*':
            numStack.push(num1 * num2);
            break;
        case '/':
            numStack.push(num1 / num2);
            break;
        }
    }
    public static boolean compare(char operation) {
//        if (opeStack.isEmpty())
//            return true;
        char last = opeStack.peek();

        switch (operation) {
        case '+':
            return false;
        case '-':
            return false;
        case '*':
            if (last == '+' || last == '-')
                return true;
            return false;
        case '/':
            if (last == '+' || last == '-')
                return true;
            return false;
        default:
            return false;
        }
    }

}