批量产生习题并用文件存储，批改练习并存储，生成100以内加法/减法的算式

以下是使用Java批量产生习题并用文件存储，批改练习并存储，生成100以内加法/减法的算式的示例代码：

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.Scanner;

public class MathExerciseGenerator {
    private static final int MAX_NUMBER = 100;
    private static final int NUM_EXERCISES = 10;

    public static void main(String[] args) {
        List<String> exercises = generateExercises(NUM_EXERCISES);
        writeToFile(exercises, "exercises.txt");

        System.out.println("请依次输入答案，每行一个答案：");
        List<String> answers = readAnswers(NUM_EXERCISES);
        writeToFile(answers, "answers.txt");

        System.out.println("批改结果：");
        checkAnswers(exercises, answers);
    }

    private static List<String> generateExercises(int num) {
        List<String> exercises = new ArrayList<>();
        Random random = new Random();
        for (int i = 0; i < num; i++) {
            int a = random.nextInt(MAX_NUMBER) + 1;
            int b = random.nextInt(MAX_NUMBER) + 1;
            boolean isAddition = random.nextBoolean();
            int result = isAddition ? a + b : a - b;
            String operator = isAddition ? "+" : "-";
            exercises.add(a + " " + operator + " " + b + " = ");
        }
        return exercises;
    }

    private static void writeToFile(List<String> lines, String fileName) {
        try (FileWriter writer = new FileWriter(new File(fileName))) {
            for (String line : lines) {
                writer.write(line + "\n");
            }
            System.out.println("已生成文件：" + fileName);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static List<String> readAnswers(int num) {
        List<String> answers = new ArrayList<>();
        Scanner scanner = new Scanner(System.in);
        for (int i = 0; i < num; i++) {
            String answer = scanner.nextLine();
            answers.add(answer);
        }
        return answers;
    }

    private static void checkAnswers(List<String> exercises, List<String> answers) {
        int numCorrect = 0;
        for (int i = 0; i < exercises.size(); i++) {
            String exercise = exercises.get(i);
            String answer = answers.get(i);
            int expected = Integer.parseInt(exercise.replaceAll("= ", ""));
            int actual = Integer.parseInt(answer);
            if (actual == expected) {
                numCorrect++;
                System.out.println(exercise + answer + " 正确");
            } else {
                System.out.println(exercise + answer + " 错误");
            }
        }
        System.out.println("总共答对 " + numCorrect + " 题，答错 " + (NUM_EXERCISES - numCorrect) + " 题。");
    }
}

在上面的代码中，我们使用了generateExercises()方法来生成指定数量的算式，并将它们写入到一个文件中；使用readAnswers()方法从控制台读取用户输入的答案，并将它们写入到另一个文件中；使用checkAnswers()方法来批改用户的答案，并输出批改结果。

注意，我们在写文件时使用了try-with-resources语句来自动关闭文件流，以避免手动关闭文件流时出现的错误。此外，我们还使用了Scanner类来读取用户的输入。