一种简单的四则运算例子

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; 
        } 
        return true; 
    } 
 
} 
 
 执行结果为：
-27
 

四则运算