JAVA nio.Files 遍历文件夹

两种方法：
1.FIles.walkFileTree()函数直接遍历此处有详细说明
2.新建DirectoryStream<Path>对象遍历当前路径，遇到文件夹再递归遍历

    public void walkFileTreeByStream(Path dir) {
        try(DirectoryStream<Path> stream = Files.newDirectoryStream(dir)){
            for(Path path : stream){
                if( Files.isDirectory() ) {
                    this.walkFileTreeByStream(path);
                }else{
                    System.out.println(path.getFileName());
                }
            }
        System.out.println(dir.getFileName());
        }catch(IOException e){
        }
    }