//获取目录下的所有文件
    private List<File> getFiles(String dir,FilenameFilter filenameFilter){
        List<File> result = new LinkedList<File>();
        File path = new File(dir);
        File[] files = path.listFiles(filenameFilter);
        for(File file : files) {
            if(file.isDirectory()) {
                List<File> fileList = getFiles(file.getAbsolutePath(),filenameFilter);
                if(CollectionUtils.isNotEmpty(fileList)){
                    result.addAll(fileList);
                }
            }
            if(file.isFile()){
                result.add(file);
            }
        }
        return result;
    }