io流

1、创建文件夹。

mkdir();和mkdirs();

        File file2 = new File("e:\demo\aa\bb\cc\dd");
        file2.mkdirs();//多层



        for(int i = 1;i<=10;i++){
            
            File file = new File("e:\demo\demo"+i);
            file.mkdir();
            for(int j = 0;j<=10;j++){
                File file1 = new File(file,"\demo"+j+".txt");
                file1.createNewFile();
            }
        }

2、获取目录下所有的文件名与文件夹名

        File file = new File("e:\");
        String [] s = file.list();
        System.out.println(Arrays.toString(s));
        for (String string : s) {
            System.out.println(string);
        }