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课后作业2

news 2026/5/11 23:04:18

动手动脑：
1.编写一个方法，使用以上算法生成指定数目（比如1000个）的随机整数。
解：import java.util.Arrays;

public class RandomNumberGenerator {

/*** 使用线性同余生成器算法生成指定数量的随机整数* @param count 要生成的随机整数数量* @param seed 随机数种子* @return 包含随机整数的数组*/
public static int[] generateRandomNumbers(int count, long seed) {if (count <= 0) {throw new IllegalArgumentException("生成数量必须大于0");}int[] randomNumbers = new int[count];long current = seed;// 线性同余生成器参数 (使用Java默认随机数生成器的参数)long a = 25214903917L;  // 乘数long c = 11L;           // 增量long m = (long) Math.pow(2, 48); // 模数 2^48for (int i = 0; i < count; i++) {// 线性同余公式: X_{n+1} = (a * X_n + c) mod mcurrent = (a * current + c) % m;// 取高32位作为随机数，转换为int类型randomNumbers[i] = (int) (current >>> 16);}return randomNumbers;
}/*** 使用系统时间作为种子生成随机数* @param count 要生成的随机整数数量* @return 包含随机整数的数组*/
public static int[] generateRandomNumbers(int count) {return generateRandomNumbers(count, System.currentTimeMillis());
}/*** 测试方法*/
public static void main(String[] args) {// 生成10个随机数int[] randomNumbers1 = generateRandomNumbers(10, 12345L);System.out.println("使用种子12345生成的10个随机数:");System.out.println(Arrays.toString(randomNumbers1));// 生成1000个随机数int[] randomNumbers2 = generateRandomNumbers(1000);System.out.println("\n使用系统时间作为种子生成的1000个随机数:");// 统计前20个System.out.print("前20个随机数: ");for (int i = 0; i < 20 && i < randomNumbers2.length; i++) {System.out.print(randomNumbers2[i] + " ");}System.out.println("...");// 基本统计信息System.out.println("\n统计信息:");System.out.println("总数: " + randomNumbers2.length);System.out.println("第一个: " + randomNumbers2[0]);System.out.println("最后一个: " + randomNumbers2[randomNumbers2.length - 1]);// 验证范围（应该是32位有符号整数范围）int min = Integer.MAX_VALUE;int max = Integer.MIN_VALUE;for (int num : randomNumbers2) {if (num < min) min = num;if (num > max) max = num;}System.out.println("最小值: " + min);System.out.println("最大值: " + max);
}

}
2. 请看以下代码，你发现了有什么特殊之处吗？

解：该段代码使用了方法重载，这段代码方法名相同；参数类型不同，参数个数不同，或者是参数类型的顺序不同。提高了代码的灵活性和可读性。
课后作业

四则运算课堂测试一
 阶段1：像二柱子那样，花二十分钟写一个能自动生成30道小学四则运算题目的 “软件”
解：import java.util.Random;

public class PrimarySchoolMathGenerator {
private static Random random = new Random();

public static void main(String[] args) {System.out.println("小学生四则运算练习题");System.out.println("====================");System.out.println();// 生成30道题目for (int i = 1; i <= 30; i++) {String exercise = generateExercise();System.out.println(i + ". " + exercise);}System.out.println();System.out.println("加油！做完记得检查哦！");
}/*** 生成一道四则运算题目*/
private static String generateExercise() {// 随机选择运算类型：0-加法，1-减法，2-乘法，3-除法int operation = random.nextInt(4);switch (operation) {case 0:return generateAddition();case 1:return generateSubtraction();case 2:return generateMultiplication();case 3:return generateDivision();default:return generateAddition();}
}/*** 生成加法题目（和不超过100）*/
private static String generateAddition() {int a = random.nextInt(50) + 1; // 1-50int b = random.nextInt(50) + 1; // 1-50// 确保和不超过100while (a + b > 100) {a = random.nextInt(50) + 1;b = random.nextInt(50) + 1;}return a + " + " + b + " = ";
}/*** 生成减法题目（结果不为负数）*/
private static String generateSubtraction() {int a = random.nextInt(50) + 10; // 10-59int b = random.nextInt(a) + 1;   // 1-a，确保结果不为负数return a + " - " + b + " = ";
}/*** 生成乘法题目（乘数不超过10，积不超过100）*/
private static String generateMultiplication() {int a = random.nextInt(10) + 1; // 1-10int b = random.nextInt(10) + 1; // 1-10// 确保积不超过100while (a * b > 100) {a = random.nextInt(10) + 1;b = random.nextInt(10) + 1;}return a + " × " + b + " = ";
}/*** 生成除法题目（确保能整除）*/
private static String generateDivision() {// 先确定除数（1-10）int divisor = random.nextInt(10) + 1;// 再确定商（1-10）int quotient = random.nextInt(10) + 1;// 被除数 = 除数 × 商int dividend = divisor * quotient;// 确保被除数不超过100while (dividend > 100) {divisor = random.nextInt(10) + 1;quotient = random.nextInt(10) + 1;dividend = divisor * quotient;}return dividend + " ÷ " + divisor + " = ";
}

}
2. 四则运算课堂测试二
阶段2：
（1）要求题目避免重复，减法不允许出现负数，乘法结果不允许出现四位数，除法必须整除不允许出现小数；
（2）实现在线实时答题，并在答题结束后，统计显示错题数，正确率；
（3）增加倒计时功能，要求在指定时间内完成测试，超时未做完视为错题。
要求上述内容编写方法实现。

解：import java.util.;
import java.util.concurrent.;

public class AdvancedMathTestSystem {
private static Random random = new Random();
private static Scanner scanner = new Scanner(System.in);
private static Set generatedExercises = new HashSet<>(); // 用于避免重复题目

// 题目和答案存储
private static List<String> exercises = new ArrayList<>();
private static List<Integer> correctAnswers = new ArrayList<>();
private static List<Integer> userAnswers = new ArrayList<>();// 测试配置
private static final int TOTAL_QUESTIONS = 10; // 题目数量
private static final int TIME_LIMIT = 60; // 时间限制（秒）public static void main(String[] args) {System.out.println("小学生四则运算在线测试系统");System.out.println("========================");System.out.println("规则说明：");System.out.println("- 共 " + TOTAL_QUESTIONS + " 道题目");System.out.println("- 时间限制: " + TIME_LIMIT + " 秒");System.out.println("- 超时未完成的题目视为错误");System.out.println("========================");// 生成不重复的题目generateUniqueExercises(TOTAL_QUESTIONS);// 开始测试（带倒计时）startTimedTest();// 显示结果统计showTestResults();scanner.close();
}/*** 生成指定数量的不重复题目*/
private static void generateUniqueExercises(int count) {int attempts = 0;int maxAttempts = count * 10; // 防止无限循环while (exercises.size() < count && attempts < maxAttempts) {String exercise = generateExercise();// 检查是否重复if (!generatedExercises.contains(exercise)) {exercises.add(exercise);generatedExercises.add(exercise);// 计算并存储正确答案int answer = calculateAnswer(exercise);correctAnswers.add(answer);}attempts++;}// 如果无法生成足够的不重复题目，用重复题目补足while (exercises.size() < count) {String exercise = generateExercise();exercises.add(exercise);int answer = calculateAnswer(exercise);correctAnswers.add(answer);}
}/*** 生成一道四则运算题目*/
private static String generateExercise() {int operation = random.nextInt(4);switch (operation) {case 0: return generateAddition();case 1: return generateSubtraction();case 2: return generateMultiplication();case 3: return generateDivision();default: return generateAddition();}
}/*** 生成加法题目（和不超过100）*/
private static String generateAddition() {int a = random.nextInt(50) + 1;int b = random.nextInt(50) + 1;// 确保和不超过100while (a + b > 100) {a = random.nextInt(50) + 1;b = random.nextInt(50) + 1;}return a + " + " + b + " = ";
}/*** 生成减法题目（结果不为负数）*/
private static String generateSubtraction() {int a = random.nextInt(50) + 10;int b = random.nextInt(a) + 1; // 确保结果不为负数return a + " - " + b + " = ";
}/*** 生成乘法题目（积不超过三位数）*/
private static String generateMultiplication() {int a = random.nextInt(20) + 1; // 1-20int b = random.nextInt(10) + 1; // 1-10// 确保积不超过三位数（即不超过999）while (a * b > 999) {a = random.nextInt(20) + 1;b = random.nextInt(10) + 1;}return a + " × " + b + " = ";
}/*** 生成除法题目（确保能整除）*/
private static String generateDivision() {int divisor = random.nextInt(10) + 1; // 1-10int quotient = random.nextInt(10) + 1; // 1-10int dividend = divisor * quotient;// 确保被除数不超过100while (dividend > 100) {divisor = random.nextInt(10) + 1;quotient = random.nextInt(10) + 1;dividend = divisor * quotient;}return dividend + " ÷ " + divisor + " = ";
}/*** 开始带倒计时的测试*/
private static void startTimedTest() {System.out.println("\n测试开始！剩余时间: " + TIME_LIMIT + " 秒");System.out.println("========================");// 创建倒计时线程CountDownLatch countDownLatch = new CountDownLatch(1);Timer timer = new Timer();timer.schedule(new TimerTask() {int remainingTime = TIME_LIMIT;@Overridepublic void run() {if (remainingTime <= 0) {System.out.println("\n\n时间到！测试结束。");countDownLatch.countDown();this.cancel();return;}// 每10秒显示一次剩余时间if (remainingTime % 10 == 0 || remainingTime <= 5) {System.out.println("剩余时间: " + remainingTime + " 秒");}remainingTime--;}}, 0, 1000); // 每秒执行一次// 记录开始时间long startTime = System.currentTimeMillis();// 开始答题for (int i = 0; i < exercises.size(); i++) {// 检查是否超时long elapsedTime = (System.currentTimeMillis() - startTime) / 1000;if (elapsedTime >= TIME_LIMIT) {System.out.println("\n时间到！未完成的题目视为错误。");// 为未答题的题目填充-1作为错误标记for (int j = i; j < exercises.size(); j++) {userAnswers.add(-1);}break;}System.out.print((i + 1) + ". " + exercises.get(i));String input = scanner.nextLine().trim();try {int answer = Integer.parseInt(input);userAnswers.add(answer);} catch (NumberFormatException e) {// 输入无效，视为错误userAnswers.add(-1);System.out.println("  输入无效，已记录为错误答案");}}// 停止计时器timer.cancel();// 确保所有题目都有用户答案while (userAnswers.size() < exercises.size()) {userAnswers.add(-1);}
}/*** 显示测试结果统计*/
private static void showTestResults() {System.out.println("\n\n测试结果统计");System.out.println("============");int correctCount = 0;List<Integer> wrongQuestions = new ArrayList<>();// 统计正确率和错题for (int i = 0; i < exercises.size(); i++) {if (userAnswers.get(i) == correctAnswers.get(i)) {correctCount++;} else {wrongQuestions.add(i + 1); // 记录错题编号}}// 显示统计信息double accuracy = (double) correctCount / exercises.size() * 100;System.out.println("总题数: " + exercises.size());System.out.println("答对题数: " + correctCount);System.out.println("答错题数: " + (exercises.size() - correctCount));System.out.printf("正确率: %.2f%%\n", accuracy);// 显示错题详情if (!wrongQuestions.isEmpty()) {System.out.println("\n错题列表:");for (int questionNum : wrongQuestions) {int index = questionNum - 1;System.out.println(questionNum + ". " + exercises.get(index) + "你的答案: " + (userAnswers.get(index) == -1 ? "未作答" : userAnswers.get(index)) + ", 正确答案: " + correctAnswers.get(index));}System.out.println("\n建议重点复习以上错题！");} else {System.out.println("\n太棒了！全部答对！");}
}/*** 计算题目的正确答案*/
private static int calculateAnswer(String exercise) {if (exercise.contains("+")) {String[] parts = exercise.split(" \\+ ");int a = Integer.parseInt(parts[0]);int b = Integer.parseInt(parts[1].split(" ")[0]);return a + b;} else if (exercise.contains("-")) {String[] parts = exercise.split(" - ");int a = Integer.parseInt(parts[0]);int b = Integer.parseInt(parts[1].split(" ")[0]);return a - b;} else if (exercise.contains("×")) {String[] parts = exercise.split(" × ");int a = Integer.parseInt(parts[0]);int b = Integer.parseInt(parts[1].split(" ")[0]);return a * b;} else if (exercise.contains("÷")) {String[] parts = exercise.split(" ÷ ");int a = Integer.parseInt(parts[0]);int b = Integer.parseInt(parts[1].split(" ")[0]);return a / b;}return 0;
}

}

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