代码

package com.itranswarp.learnjava;

import java.io.File;
import java.io.IOException;

/**
 * Learn Java from https://www.liaoxuefeng.com/
 * 
 * @author liaoxuefeng
 */
public class Main {

	public static void main(String[] args) throws IOException {
		File currentDir = new File("./Documents"); // 所需文件已手动创建在本地目录
		System.out.println("Documents/");
		listDir(currentDir.getCanonicalFile());
	}

	static int depth = 1;
	static void listDir(File dir) {
		// TODO: 递归打印所有文件和子文件夹的内容
		File[] fs = dir.listFiles();
		String blank = "  ";
		blank = blank.repeat(depth);
		if (fs != null) {
			for (File f : fs) {
				if (f.isDirectory()) {
					System.out.println(blank + f.getName() + "/");
					depth ++;
					listDir(f);
					depth --;
				}
				if (f.isFile()) {
					System.out.println(blank + f.getName());
				}
			}
		}
	}
}

输出

Documents/

  other/

  ppt/

  word/

    1.docx

    2.docx

    work/

      abc.doc