如何使用java搜索文件中存在的日期格式20180603？

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class DateSearch {
    private static final String DATE_REGEX = "\\d{8}";

    public static void main(String[] args) {
        String folderPath = "your_folder_path";
        List<String> matchingDates = new ArrayList<>();

        searchDatesInFolder(folderPath, matchingDates);

        if (!matchingDates.isEmpty()) {
            System.out.println("Matching dates found:");
            for (String date : matchingDates) {
                System.out.println(date);
            }
        } else {
            System.out.println("No matching dates found.");
        }
    }

    private static void searchDatesInFolder(String folderPath, List<String> matchingDates) {
        File folder = new File(folderPath);

        if (folder.exists() && folder.isDirectory()) {
            File[] files = folder.listFiles();
            if (files != null) {
                for (File file : files) {
                    if (file.isFile()) {
                        searchDatesInFile(file, matchingDates);
                    } else if (file.isDirectory()) {
                        searchDatesInFolder(file.getAbsolutePath(), matchingDates);
                    }
                }
            }
        }
    }

    private static void searchDatesInFile(File file, List<String> matchingDates) {
        try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
            String line;
            Pattern pattern = Pattern.compile(DATE_REGEX);

            while ((line = reader.readLine()) != null) {
                Matcher matcher = pattern.matcher(line);
                while (matcher.find()) {
                    matchingDates.add(matcher.group());
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}