Java Part10 Mission3

import java.io.File;
import java.util.Objects;
import java.util.Scanner;


public class Q1 {
    
    public Q1(String filename) {
        File file = new File(filename);
        if (!file.exists()) {
            System.out.println("你输入的"+file.getName()+"目录有误。");
        } else {
            for (String name : Objects.requireNonNull(file.list())) {
                System.out.println(name);
            }
        }
    }

    public static void main(String[] args) {
        String filename = new Scanner(System.in).nextLine();
        new Q1(filename);
    }
}

GBK编码中文占两个字节，UTF-8编码中文三个字节，在本程序中对使用UTF-8的编码的txt文件进行处理。

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;


public class Q2 {
    
    public Q2(String filename) throws IOException {
        File file = new File(filename);
        RandomAccessFile raf = new RandomAccessFile(file,"r");
        long length = raf.length();
        StringBuffer buffer = new StringBuffer();
        while (length > 0) {
            length--;
            // 转到length的位置
            raf.seek(length);
            int c = (int)raf.readByte();
            if (c >= 0 && c <= 255) {
                buffer.append((char)c);
            }else {
                // UTF-8编码中文三个字节
                length = length - 2;
                // 对GBK编码的txt文件处理
                // length--;
                raf.seek(length);
                byte[] character = new byte[3];
                // GBK编码
                // byte[] character = new byte[2];
                // 读取中文的三个字节
                raf.read(character);
                buffer.append(new String(character));
            }
        }
        System.out.println(buffer);
    }

    public static void main(String[] args) {
        try {
            new Q2("D:/test.txt");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}