一、单层多个

代码实现如下：

public class Main {public static void main(String[] args) {//在D盘中创建File file = new File("D:"+File.separator+"docum");file.mkdir();//在D盘中的docum目录中创建file = new File("D:\\docum"+ File.separator+"C");file.mkdir();file = new File("D:\\docum"+ File.separator+"java");file.mkdir();file = new File("D:\\docum"+ File.separator+"python");file.mkdir();}
}

二、多层单个

public class Main {public static void main(String[] args) {File file = new File("D:"+File.separator+"One"+File.separator+"Two"+File.separator+"Three");file.mkdirs();}
}

三、多层多个

public class Lx02 {public static void main(String[] args) {File file = new File("D:"+File.separator+"One"+File.separator+"Two"+File.separator+"Three");file.mkdirs();file = new File("D:\\One\\Two"+ File.separator+"a"+ File.separator+"b");file.mkdirs();}
}