import java.io.File;

public class Test {
    public static void main(String[] args) {
        File file = new File("./dir");
        // 判断文件夹是否存在
        if (!file.exists()) {
            // 创建文件夹
            if (!file.mkdirs()) {
                System.out.println("创建文件夹失败");
            }
        } else {
            // 删除文件夹
            if (!file.delete()) {
                System.out.println("删除文件夹失败");
            }
        }
    }
}

import java.io.File;

public class Test {
    public static void main(String[] args) {
        // 获取当前目录
        String dir = System.getProperty("user.dir");
        System.out.println(dir);
        // 枚举当前目录中的文件
        File file = new File(dir);
        String[] children = file.list();
        if (children != null) {
            for (String name : children) {
                System.out.println(name);
            }
        }
    }
}

import java.io.*;

public class Test {
    public static void main(String[] args) {
        // 写入文件
        try {
            OutputStream stream = new FileOutputStream("./user.txt");
            OutputStreamWriter writer = new OutputStreamWriter(stream);
            writer.write("你好");
            writer.flush();
            writer.close();
            stream.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        // 读取文件
        try {
            InputStream stream = new FileInputStream("./user.txt");
            InputStreamReader reader = new InputStreamReader(stream);
            BufferedReader bufferedReader = new BufferedReader(reader);
            String text = bufferedReader.readLine();
            System.out.println(text);
            bufferedReader.close();
            reader.close();
            stream.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}