先上代码：

　　 @SneakyThrows  //合并操作，最终文件不包含结束标识，方便多次合并
    private static void mergeM3U8File(String source, String target) {
        
        //读取target
        List<String> sl = new ArrayList<>();
        try (BufferedReader reader = new BufferedReader(new FileReader(source))) {
            String line;
            while ((line = reader.readLine()) != null) {
                sl.add(line);
            }
        }
        //读取source
        List<String> tl = new ArrayList<>();
        try (BufferedReader reader = new BufferedReader(new FileReader(target))) {
            String line;
            while ((line = reader.readLine()) != null) {
                tl.add(line);
            }
        }
        //合并且统一ts文件名
        String filename = target.replace(dir,"");
        filename = filename.replace(".m3u8","");
        Long order = 0l;
        if (tl.size() <= 0) {
            for (String s : sl) {
                if(s.startsWith("#")) tl.add(s);
                else {
                    tl.add(filename + order + ".ts");
                    log.info("转存文件 {}{} 存在状态 {}", dir, s, Files.exists(Paths.get(dir + s)));
                    Files.copy(Paths.get(dir + s), Paths.get(dir + filename + order + ".ts"));
                    Files.delete(Paths.get(dir + s));
                    order++;
                }
            }
        }
        else {
            //删除结束段落
            if(tl.get(tl.size()-1).startsWith("#EXT-X-ENDLIST")) {
                tl.remove(tl.size() - 1);
            }
            //获取文件序号（dir+filename+order.ts）
            String s = tl.get(tl.size() - 1);
            s = s.replace(".ts","");
            s = s.replace(filename,"");
            order = Long.parseLong(s);
            //sl处理 获取头部标识的下标并移除头部
            int i = 0;
            for (i = 0; i < sl.size(); i++) {
                if (sl.get(i).startsWith("#EXTINF")) break;
            }
            for (int j = 0; j < i; j++) {
                sl.remove(0);
            }
            sl.remove(sl.size() - 1);
            tl.add("#EXT-X-DISCONTINUITY");
            //sl文件内容写入tl
            for (int j = 0; j < sl.size(); j++) {
                String s1 = sl.get(j);
                if(s1.startsWith("#EXTINF")) //#EXTINF
                    tl.add(s1);
                else//按规则写入文件索引
                {
                    order++;
                    tl.add(filename + order + ".ts");
                    log.info("转存文件 {}{} 存在状态 {}",dir,s1,Files.exists(Paths.get(dir + s1)));
                    Files.copy(Paths.get(dir + s1), Paths.get(dir + filename + order + ".ts"));
                    Files.delete(Paths.get(dir + s1));
                }
            }
        }
        //生成新的buffer
        StringBuffer buffer = new StringBuffer();
        for (String t : tl) {
            buffer.append(t).append(System.lineSeparator());
        }
        //写入文件
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(target))) {
            writer.write(buffer.toString());
        }
        //清除source
        Files.delete(Paths.get(source));
    }

    @SneakyThrows //给m3u8文件添加结束标识
    private static void endM3u8(String m3u8) {
        List<String> sl = new ArrayList<>();
        try (BufferedReader reader = new BufferedReader(new FileReader(m3u8))) {
            String line;
            while ((line = reader.readLine()) != null) {
                sl.add(line);
            }
        }
        sl.add("#EXT-X-ENDLIST");
        //生成新的buffer
        StringBuffer buffer = new StringBuffer();
        for (String t : sl) {
            buffer.append(t).append(System.lineSeparator());
        }
        //写入文件
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(m3u8))) {
            writer.write(buffer.toString());
        }

    }

关于m3u8文件的说明：

- #EXTM3U：文件头，标识这是一个M3U8文件。
- #EXT-X-VERSION：表示M3U8的版本号。
- #EXT-X-TARGETDURATION：表示每个分段的最长时间（以秒为单位）。
- #EXT-X-MEDIA-SEQUENCE：表示播放列表中的第一个分段的编号。
- #EXTINF：表示当前分段的播放时间长度（以秒为单位）和URI