代码：

import java.io.*;

public class FileExport {

    public static void main(String[] args) throws Exception {
        //文件读取路径
        File dir = new File("/Users/****/Documents/IdeaProjects/video-analysis-master/modules/bizmain/bizmain-provider/src/main/java/com/dtwave/aihub/bizmain/service");

        //文件输出路径
        File target = new File("/Users/*****/Documents/service.txt");
        BufferedWriter bw = new BufferedWriter(new FileWriter(target));

        StringBuffer sb = new StringBuffer();
        loopRead(dir, sb);
        write(sb.toString(), bw);
    }

    // 遍历文件夹下所有文件
    private static void loopRead(File dir, StringBuffer sb) {
        File[] files = dir.listFiles();
        if (files != null) {
            for (File file : files) {
                if (file.isDirectory()) {
                    loopRead(file, sb);
                } else {
                    if (file.length() != 0) {
                        sb.append(readFileToString(file));
                    }
                }
            }
        }
    }

    //读取文件里面的内容
    private static String readFileToString(File file) {
        BufferedReader br = null;
        StringBuilder sb = new StringBuilder();
        try {
            br = new BufferedReader(new FileReader(file));
            String line = null;
            while ((line = br.readLine()) != null) {
                String s = line.trim();
                if (s.length() == 0) {
                    continue;
                }
                if (s.startsWith("/") || s.startsWith("*")) {
                    continue;
                }
                sb.append(line).append("\n");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (br != null) {
                    br.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return sb.toString();

    }

    //将读取的路径以及相应的内容写入指定的文件
    private static void write(String str, Writer writer) {
        try {
            writer.write(str);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {

            try {
                if (writer != null) {
                    writer.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }

    }
}