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• [ ] 개발환경 만들기

Code

@PostMapping("/calculator")
public String calculatorProc(HttpServletRequest req, HttpSession session, Model model) {
    String num_ = req.getParameter("num");
    String op_ = req.getParameter("op");
    Object obj = session.getAttribute("stack");
    Stack<String> stack = (obj == null) ? new Stack<>() : (Stack) obj;

    if (num_ != null) {
        if (stack.isEmpty()) {
            stack.push(num_);
        } else {
            String element = stack.pop();
            if (element.equals("/") || element.equals("*")
                    || element.equals("-") || element.equals("+")) {
                stack.push(element);
                stack.push(num_);
            } else {
                num_ = element + num_;
                stack.push(num_);
            }
        }
        session.setAttribute("stack", stack);
        model.addAttribute("eval", getEval(stack));
    } else if (op_ != null && !op_.equals("=")) {
        if (op_.equals("C")) {
            if (stack.isEmpty())
                ;
            else {
                String s = stack.pop();
                if (s.length() > 1) {
                    s = s.substring(0, s.length() - 1);
                    stack.push(s);
                }
            }
        } else
            stack.push(op_);
        session.setAttribute("stack", stack);
        model.addAttribute("eval", getEval(stack));
    } else {
        int result = 0;
        int num2 = Integer.parseInt(stack.pop());
        String op = stack.pop();
        int num1 = Integer.parseInt(stack.pop());
        switch (op) {
            case "+":
                result = num1 + num2;
                break;
            case "-":
                result = num1 - num2;
                break;
            case "*":
                result = num1 * num2;
                break;
            case "/":
                result = (int) (num1 / num2);
                break;
            default:
                result = 0;
        }
        session.removeAttribute("stack");
        model.addAttribute("eval", result);
    }
    return "08.calculator";
}

String getEval(Stack<String> stack) {
    String eval = "";
    for (String s : stack)
        eval += s + " ";
    return eval;
}