Random operatorChoice = new Random();
int operator = operatorChoice.nextInt(3); // 生成 0, 1, 或 2

String operatorSwitch;
switch (operator) { // 根據(jù) operator 的值確定運(yùn)算符
    case 0: operatorSwitch = "+"; break;
    case 1: operatorSwitch = "-"; break;
    case 2: operatorSwitch = "*"; break;
    // case 3: operatorSwitch = "/"; // 注意：nextInt(3) 不會返回 3
    default: operatorSwitch = ""; break;
}

// 第一次使用 operatorSwitch
System.out.println("問題 1, 計算: " + firstNumbereasy + operatorSwitch + secondNumbereasy);

// 第二次使用 operatorSwitch
System.out.println("問題 2, 計算: " + anotherFirstNumber + operatorSwitch + anotherSecondNumber);

import java.util.Random;
import java.util.Scanner;

public class MathQuiz {

    private static final Random randGen = new Random(); // 推薦將Random實(shí)例作為類的成員，避免重復(fù)創(chuàng)建

    /**
     * 生成一個隨機(jī)的數(shù)學(xué)運(yùn)算符 (+, -, *, /)。
     * @return 隨機(jī)運(yùn)算符字符串。
     */
    public static String getRandomOperator() {
        // nextInt(4) 會生成 0, 1, 2, 3，從而包含除法
        int operatorIndex = randGen.nextInt(4); 

        switch (operatorIndex) {
            case 0: return "+";
            case 1: return "-";
            case 2: return "*";
            case 3: return "/";
            default: return "+"; // 理論上不會執(zhí)行到，作為備用
        }
    }

    /**
     * 根據(jù)運(yùn)算符和兩個操作數(shù)計算結(jié)果。
     * @param num1 第一個操作數(shù)
     * @param num2 第二個操作數(shù)
     * @param operator 運(yùn)算符字符串
     * @return 計算結(jié)果
     */
    public static int calculateResult(int num1, int num2, String operator) {
        switch (operator) {
            case "+": return num1 + num2;
            case "-": return num1 - num2;
            case "*": return num1 * num2;
            case "/": 
                if (num2 == 0) {
                    // 處理除零錯誤，這里簡單返回0或拋出異常
                    System.err.println("錯誤：除數(shù)不能為零。");
                    return 0; 
                }
                return num1 / num2;
            default: return 0; // 未知運(yùn)算符
        }
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int firstNumbereasy;
        int secondNumbereasy;
        String currentOperator;
        int expectedResult;
        int userAnswer;

        // --- 問題 1 ---
        firstNumbereasy = randGen.nextInt(9) + 2; // 2-10
        secondNumbereasy = randGen.nextInt(firstNumbereasy - 1) + 1; // 1 到 firstNumbereasy-1

        currentOperator = getRandomOperator(); // 為問題 1 生成新的隨機(jī)運(yùn)算符
        expectedResult = calculateResult(firstNumbereasy, secondNumbereasy, currentOperator);

        System.out.println("問題 1, 計算: " + firstNumbereasy + " " + currentOperator + " " + secondNumbereasy + " = ?");
        userAnswer = scanner.nextInt();

        if (userAnswer == expectedResult) {
            System.out.println("回答正確！");
        } else {
            System.out.println("回答錯誤。正確答案是：" + expectedResult);
        }

        // --- 問題 2 ---
        // 重新生成新的操作數(shù)
        firstNumbereasy = randGen.nextInt(9) + 2; 
        secondNumbereasy = randGen.nextInt(firstNumbereasy - 1) + 1; 

        currentOperator = getRandomOperator(); // 為問題 2 生成新的隨機(jī)運(yùn)算符
        expectedResult = calculateResult(firstNumbereasy, secondNumbereasy, currentOperator);

        System.out.println("問題 2, 計算: " + firstNumbereasy + " " + currentOperator + " " + secondNumbereasy + " = ?");
        userAnswer = scanner.nextInt();

        if (userAnswer == expectedResult) {
            System.out.println("回答正確！");
        } else {
            System.out.println("回答錯誤。正確答案是：" + expectedResult);
        }

        scanner.close();
    }
}