文件拼接

import java.io.*;
import java.nio.channels.FileChannel;
import java.util.ArrayList;
import java.util.List;

public class Main {
    private static String FILE_PATH = "D:\\BaiduNetdiskDownload\\test";
    private static String DEST_FILE_PATH = "D:\\BaiduNetdiskDownload\\3.md";


    public static void main(String[] args) throws IOException {

        ArrayList<String> fileNames = (ArrayList<String>) getFileNames(new File(FILE_PATH), new ArrayList<>());
        BufferedReader br = null;
        PrintWriter pw = null;
        try {
            pw = new PrintWriter(DEST_FILE_PATH);
            for (String fileName : fileNames) {
                br = new BufferedReader(new InputStreamReader(new FileInputStream(FILE_PATH + File.separator + fileName)));
                String line;
                while ((line = br.readLine()) != null) {
                    if (line.indexOf("####") > -1) {
                        line = line.replaceAll("####", "#####");
                    } else if (line.indexOf("###") > -1) {
                        line = line.replaceAll("###", "####");
                    } else if (line.indexOf("##") > -1) {
                        line = line.replaceAll("##", "###");
                    } else if (line.indexOf("#") > -1) {
                        line = line.replaceAll("#", "##");
                    }
                    pw.println(line);
                }
                br.close();
            }
        } catch (FileNotFoundException e) {
            throw new RuntimeException(e);
        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            br.close();
            pw.close();
        }
        System.out.println("Hello world!");
    }

    private static List<String> getFileNames(File file, List<String> fileNames) {
        File[] files = file.listFiles();
        for (File f : files) {
            if (f.isDirectory()) {
                getFileNames(f, fileNames);
            } else {
                fileNames.add(f.getName());
            }
        }
        return fileNames;
    }

    private void test() throws IOException {
        ArrayList<String> fileNames = (ArrayList<String>) getFileNames(new File(FILE_PATH), new ArrayList<>());
        BufferedReader br = null;
        PrintWriter pw = null;
        FileChannel inputChannel = null;
        FileChannel outputChannel = null;
        try {
            outputChannel = new FileOutputStream(DEST_FILE_PATH).getChannel();
            long index = 0;
            for (String fileName : fileNames) {
                inputChannel = new FileInputStream(FILE_PATH + File.separator + fileName).getChannel();
                outputChannel.transferFrom(inputChannel, index, inputChannel.size());
                index += inputChannel.size();
            }
        } catch (FileNotFoundException e) {
            throw new RuntimeException(e);
        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            inputChannel.close();
            outputChannel.close();
        }

        System.out.println("Hello world!");
    }

}