【基础版】整数加减乘除计算器

package com.yeezhao.common.elt;

import java.util.Stack;
import java.util.StringTokenizer;

/**
 * 正整数计算器
 * 
 * @author Administrator -> junhong
 * @since 2016年12月13日 下午1:22:40
 */
public class CaculatorSimulate {

    private Stack<Character> operator = new Stack<>(); // 操作符
    private Stack<Integer> operand = new Stack<>(); // 操作数 0-9

    public void testCaculate() {
    }

    public void testOutput() {

    }

    /**
     * 返回计算结果
     * 
     * @param exp
     *            正整数的加减乘除表达式
     * @return
     */
    public Integer caculate(String exp) {
        if (exp == null || exp.isEmpty()) {
            System.out.println("invalid exp!");
            return 0;
        }
        StringTokenizer arr = new StringTokenizer(exp, "+-/*()", true);
        while (arr.hasMoreTokens()) {
            String text = arr.nextToken().trim();
            if (text.length() == 0) { // fix '(('
                continue;
            }
            char c = text.charAt(0);
            if (c == '+' || c == '-') {
                while (!operator.isEmpty() && ((operator.peek() == '+') || (operator.peek() == '-')
                        || (operator.peek() == '/') || (operator.peek() == '*'))) {
                    oper(operator, operand);
                }
                operator.push(c);
            } else if (c == '/' || c == '*') {
                while (!operator.isEmpty() && ((operator.peek() == '/') || (operator.peek() == '*'))) {
                    oper(operator, operand);
                }
                operator.push(c);

            } else if (c == '(') {
                operator.push(c);
            } else if (c == ')') {
                while (operator.peek() != '(') {
                    oper(operator, operand);
                }
                operator.pop();
            } else {
                operand.push(Integer.parseInt(text));
            }
        }

        while (!operator.isEmpty()) {
            oper(operator, operand);
            ;
        }
        return operand.pop();
    }

    public void oper(Stack<Character> operator, Stack<Integer> operand) {
        Integer num1 = operand.pop();
        Integer num2 = operand.pop();
        Character oper = operator.pop();
        Integer ret = 0;
        if (oper == '-')
            ret = num2 - num1;
        if (oper == '+')
            ret = num2 + num1;
        if (oper == '*')
            ret = num2 * num1;
        if (oper == '/') {
            if (num1 == 0) {
                System.out.println("'0' can not be divided!");
            } else {
                ret = num2 / num1;
            }
        }
        operand.push(ret);

    }

    public static void main(String[] args) {
        String[] exps = { "1+2", "3 * (4 + 5)", "(4 + 5) / 3 + (1 + 2*1)" };
        System.out.println("---***---");
        for (String exp : exps) {
            int ans = new CaculatorSimulate().caculate(exp);
            System.out.println(exp + " ==> " + ans);
        }
    }

}