Java中生成多个独立随机运算符的实践指南

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

String operatorSwitch;
switch (operator) { // 根据 operator 的值确定运算符
    case 0: operatorSwitch = "+"; break;
    case 1: operatorSwitch = "-"; break;
    case 2: operatorSwitch = "*"; break;
    // case 3: operatorSwitch = "/"; // 注意：nextInt(3) 不会返回 3
    default: operatorSwitch = ""; break;
}

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

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

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

public class MathQuiz {

    private static final Random randGen = new Random(); // 推荐将Random实例作为类的成员，避免重复创建

    /**
     * 生成一个随机的数学运算符 (+, -, *, /)。
     * @return 随机运算符字符串。
     */
    public static String getRandomOperator() {
        // nextInt(4) 会生成 0, 1, 2, 3，从而包含除法
        int operatorIndex = randGen.nextInt(4); 

        switch (operatorIndex) {
            case 0: return "+";
            case 1: return "-";
            case 2: return "*";
            case 3: return "/";
            default: return "+"; // 理论上不会执行到，作为备用
        }
    }

    /**
     * 根据运算符和两个操作数计算结果。
     * @param num1 第一个操作数
     * @param num2 第二个操作数
     * @param operator 运算符字符串
     * @return 计算结果
     */
    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) {
                    // 处理除零错误，这里简单返回0或抛出异常
                    System.err.println("错误：除数不能为零。");
                    return 0; 
                }
                return num1 / num2;
            default: return 0; // 未知运算符
        }
    }

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

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

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

        currentOperator = getRandomOperator(); // 为问题 1 生成新的随机运算符
        expectedResult = calculateResult(firstNumbereasy, secondNumbereasy, currentOperator);

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

        if (userAnswer == expectedResult) {
            System.out.println("回答正确！");
        } else {
            System.out.println("回答错误。正确答案是：" + expectedResult);
        }

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

        currentOperator = getRandomOperator(); // 为问题 2 生成新的随机运算符
        expectedResult = calculateResult(firstNumbereasy, secondNumbereasy, currentOperator);

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

        if (userAnswer == expectedResult) {
            System.out.println("回答正确！");
        } else {
            System.out.println("回答错误。正确答案是：" + expectedResult);
        }

        scanner.close();
    }
}