2022-08-08 The fifth group Gu Xiangquan study notes day31-collection-IO stream-File class

File类

file是什么？ —> 文件和目录路径名的抽象表示形式.

1. 包路径：java.io.File
2. 继承关系：File —> Object
3. 构造方法
   
   4.方法

常用方法

Not empty directory delete

With the creation of a file directory

编写一个简易的cmd

package com.jsoft.io.file;

import org.junit.Test;

import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Scanner;

public class CMD {
    
    private static String currentDir;  // 当前目录路径
    private static String userIn;       // 用户输入内容
    private static Scanner sc;

    static {
    
        currentDir = System.getProperty("user.dir");
        sc = new Scanner(System.in);
    }

    // 切换路径
    private static boolean cd(String dirName) throws IOException {
    

        // 当前路径(currentDir)+相对路径
        File file = new File(currentDir + "\\" + dirName);
        // 如果是绝对路径
        if(dirName.contains(":")) {
    
            file = new File(dirName);
        }

        // 切换当前目录
        if(".".equals(dirName)) {
    
            return true;
        }
        // 切换到上级目录
        if("..".equals(dirName)) {
    

            File fatherFile = new File(currentDir).getParentFile();
            if(fatherFile == null) {
    
                return false;
            }
            currentDir = fatherFile.getCanonicalPath();
            return true;
        }

        // 如果不是目录
        if(isFile(file)) {
    
            System.out.println("目录名称无效");
            return false;
        }

        // 如果文件不存在
        if(!file.exists()) {
    
            System.out.println("系统找不到指定的路径.");
            return false;
        }

        // 文件存在
        currentDir = file.getCanonicalPath();
        return true;

    }

    // 创建文件或目录
    private static boolean md(String cdContent) throws IOException {
    
        File file = new File(currentDir + "\\" + cdContent);

        // 如果是绝对路径
        if(cdContent.contains(":")) {
    
            file = new File(cdContent);
        }

        // 如果是文件(Now can't handle with directory file)
        if(isFile(file)) {
    
            file.createNewFile();
        } else {
    
            file.mkdirs();
        }
        return true;

    }



    // Print the current path all the files in the directory information
    private static void dir() {
    
        File[] files = new File(currentDir).listFiles();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm");
        long byteNum = 0;

        if(files.length == 0) {
    
            System.out.println("当前目录为空");
            return;
        }
        // Here is a statistical folder - accessor to size of
        for(File file : files) {
    
            byteNum += file.length();
            StringBuilder sb = new StringBuilder();
            sb.append(sdf.format(new Date(file.lastModified())));
            sb.append("\t");
            sb.append(file.isDirectory() ? "<DIR>" : "\t");
            sb.append("\t");
            sb.append(file.length());
            sb.append("\t");
            sb.append(file.getName());
            System.out.println(sb);
        }
        System.out.println(files.length + " 个文件");
        System.out.println(byteNum + " 字节");

    }

    private static boolean rd(String rdContent) throws IOException {
    
        File file = new File(currentDir + "\\" + rdContent);

        // 如果是绝对路径
        if(rdContent.contains(":")) {
    
           file = new File(rdContent);
        }

        // 如果是文件
        if (isFile(file)) {
    
            file.delete();
            return true;
        } else {
    
            // No support for multistage folder is not empty folders and delete
            file.delete();
            return true;
        }
    }


    // Get the user to type
    private static String commindLine() {
    
        System.out.print(currentDir + ">");
        userIn = sc.nextLine();
        return userIn;
    }

    // 显示帮助信息
    private static void help() {
    
        // cd
        StringBuilder sb = new StringBuilder();
        sb.append("cd命令");
        sb.append("\n");
        sb.append("语法格式：cd 文件路径");
        sb.append("\t");
        sb.append("改变当前目录(支持相对路径和绝对路径)");
        System.out.println(sb);
        System.out.println("---------------------------------------");
        // dir
        sb = new StringBuilder();
        sb.append("dir命令");
        sb.append("\t");
        sb.append("未实现功能：Query list of byte size,Statistics of the number of files and directories,对./..显示");
        sb.append("\n");
        sb.append("语法格式：dir");
        sb.append("\t");
        sb.append("列出当前目录的所有文件");
        System.out.println(sb);
        System.out.println("---------------------------------------");

        // md
        sb = new StringBuilder();

        sb.append("md命令");
        sb.append("\t");
        sb.append("未实现功能：创建带目录的文件");
        sb.append("\n");
        sb.append("语法格式：md 文件路径");
        sb.append("\t");
        sb.append("创建文件(支持相对路径和绝对路径)");
        System.out.println(sb);
        System.out.println("---------------------------------------");

        // rd
        sb = new StringBuilder();
        sb.append("rd命令");
        sb.append("\t");
        sb.append("未实现功能：To not empty directory delete");
        sb.append("\n");
        sb.append("语法格式：rd 文件路径");
        sb.append("\t");
        sb.append("删除文件(支持相对路径和绝对路径)");
        System.out.println(sb);
        System.out.println("---------------------------------------");
        sb = new StringBuilder();
        sb.append("exit");

        sb.append("\t");
        sb.append("退出cmd");
        System.out.println(sb);
        System.out.println("---------------------------------------");


    }

    // 判断File是否是文件,当路径中包含“.”时,我们认为这个file是一个文件
    private static boolean isFile(File file) throws IOException {
    
        // 当路径中存在.时,我们认为这个File是一个文件
        if(file.getCanonicalPath().contains(".")) {
    
            return true;
        }
        return false;
    }

    public static void main(String[] args) throws IOException {
    


        System.out.println("Microsoft Windows [版本 10.0.18363.1556]\n" +
                "(c) 2019 Microsoft Corporation.保留所有权利.\n");
        System.out.println("输入help查看帮助信息\n\n");

        while(true) {
    
           // Get the user to type
           String userIn = commindLine();

           if(userIn.startsWith("cd")) {
    
               String[] split = userIn.split(" ");
               if(split.length != 2) {
    
                   System.out.println("格式错误");
                   continue;
               }
               String dirName = split[1];
               cd(dirName);

           } else if(userIn.startsWith("dir")) {
    
               dir();
           } else if(userIn.startsWith("md")) {
    
               String[] split = userIn.split(" ");
               String cdContent = split[1];
               md(cdContent);
           } else if(userIn.startsWith("rd")) {
    
               String[] split = userIn.split(" ");
               String rdContent = split[1];
               rd(rdContent);

           }else if("help".equals(userIn)) {
    
               help();
           }else if("exit".equals(userIn)) {
    
               break;
           } else {
    
               System.out.println(userIn + "不是内部或外部命令,也不是可运行的程序或批处理文件.");
           }
       }

    }

}