1. 练习一

在当前模块下的 text 文件夹中创建一个 io.txt 文件

import java.io.File;
import java.io.IOException;public class Practice1 {public static void main(String[] args) {File file = new File("D:\\kaifamiao");File file1 = new File(file, "text\\ebook\\IO");File text = new File(file1, "io.txt");// 判断文件夹是否存在，如果不存在则建立if (!file1.exists()) {boolean mkdir = file1.mkdirs();System.out.println(mkdir);  // true}try {text.createNewFile();} catch (IOException e) {throw new RuntimeException(e);}}
}

2. 练习二

删除一个多级文件夹

import java.io.File;public class DeleteMultFilesPractice2 {public static void main(String[] args) {File file = new File("D:\\kaifamiao\\text");delete(file);}public static void delete(File file) {if (file.exists()) {File[] files = file.listFiles();if (files != null && files.length != 0) {for (File f : files) {if (f.isDirectory()) {delete(f);} else {f.delete();}}}file.delete();System.out.println("目录已删除：" + file.getAbsolutePath());} else {System.out.println("目录不存在：" + file.getAbsolutePath());}}
}

3. 练习三

统计一个文件夹中每种文件的个数并打印(不考虑目录)

import java.io.File;
import java.util.HashMap;public class StatisticalFiles3 {public static void main(String[] args) {File file = new File("D:\\桌面\\我爱学习");String[] files = file.list();HashMap<String,Integer> hashMap = new HashMap<>();assert files != null;for (String s : files) {if (s.contains(".")) {int lastDotIndex = s.lastIndexOf(".");String extension = s.substring(lastDotIndex + 1);hashMap.put(extension,hashMap.getOrDefault(extension, 0) + 1);} else {hashMap.put("文件",hashMap.getOrDefault("文件", 0) + 1);}}System.out.println(hashMap);}
}

4. 练习四

计算出磁盘上指定文件夹的实际大小

import java.io.File;public class StatisticalFileSize4 {public static void main(String[] args) {long l = fileSize(new File("D:\\桌面\\我爱学习\\网页练习\\建党95"));System.out.println(l);}/*** 计算出磁盘上指定文件夹的实际大小* @param file*/public static long fileSize (File file) {File[] files = file.listFiles();long count = 0;if (files != null && files.length != 0) {for (File f : files) {if (f.isDirectory()) {count += fileSize(f);} else {System.out.println(f.toString()+ f.length());count += f.length();}}}return count;}
}