public class Calculator {
    private double result; // 存儲計(jì)算結(jié)果
    public Calculator() {
        result = 0;
    }
    public double getResult() {
        return result;
    }
    public void add(double num) {
        result += num;
    }
    public void subtract(double num) {
        result -= num;
    }
    public void multiply(double num) {
        result *= num;
    }
    public void divide(double num) {
        if (num == 0) {
            System.out.println("Error: divide by zero");
        } else {
            result /= num;
        }
    }
    public void clear() {
        result = 0;
    }
}

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Calculator calculator = new Calculator();
        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.println("請輸入數(shù)字和操作符（+、-、*、/），用空格分隔，輸入q退出：");
            String input = scanner.nextLine();
            if (input.equals("q")) {
                break;
            }
            String[] tokens = input.split(" ");
            double num = Double.parseDouble(tokens[0]);
            char op = tokens[1].charAt(0);
            switch (op) {
                case '+':
                    calculator.add(num);
                    break;
                case '-':
                    calculator.subtract(num);
                    break;
                case '*':
                    calculator.multiply(num);
                    break;
                case '/':
                    calculator.divide(num);
                    break;
                default:
                    System.out.println("Error: invalid operator");
            }
            System.out.println("Result: " + calculator.getResult());
        }
    }
}