public class Lesson8LevelOneTaskThree {
    public static void main(String[] args) {
        File folder = new File("Main_Folder");
        folder.mkdirs();
        displayListDirectories(folder);
        }

    public static void displayListDirectories(File folder) {

        //Для примера создаем три папки в папке Main_folder

        File folderOne = new File(folder,"Music");
        folderOne.mkdirs();
        File folderTwo = new File(folder,"Letters");
        folderTwo.mkdir();
        File folderOThree = new File(folder,"Documents");
        folderOThree.mkdir();

        String[] arrayFolder = folder.list();
        for (String s : arrayFolder) {
            System.out.println(s);
        }
    }
}