math_paper/src/HistoryManager.java

import java.util.HashSet;
import java.util.Set;
import java.io.*;

public class HistoryManager {
    private final Set<String> existingQuestions = new HashSet<>();

    public HistoryManager(String username) {
        File folder = new File(username);
        if (!folder.exists() && !folder.mkdir()) {
            System.err.println("无法创建文件夹: " + username);
        }
        File[] files = folder.listFiles();
        if (files != null) {
            for (File file : files) {
                if (file.isFile() && file.getName().endsWith(".txt")) {
                    try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
                        String line;
                        while ((line = reader.readLine()) != null) {
                            line = line.trim();
                            if (line.matches("^\\d+\\..*")) {
                                int dotIndex = line.indexOf('.');
                                String question = line.substring(dotIndex + 1).trim();
                                if (question.endsWith("=")) {
                                    question = question.substring(0, question.length() - 1).trim();
                                }
                                existingQuestions.add(question);
                            }
                        }
                    } catch (IOException e) {
                        System.err.println("读取文件出错: " + file.getName());
                    }
                }
            }
        }
    }

    public boolean isDuplicate(String question) {
        return existingQuestions.contains(question);
    }

    public void add(String question) {
        existingQuestions.add(question);
    }
}