1. 创建文件，createNewFile
   exists() 判断文件是否存在
   delete() 删除文件

package xyz.liangshuai.demo1;

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

public class Test1 {

    public static void main(String[] args) {
        //调用有参构造创建对象
        File f = new File("E:/abc.txt");
        
        try {
            if (!f.exists()) {//判断文件是否存在
                f.createNewFile();//创建文件
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        f.delete();
    }
}

2. 创建文件夹，单层目录用mkdir()，双层目录用mkdirs()

package xyz.liangshuai.demo1;

import java.io.File;

public class Test2 {

    public static void main(String[] args) {
        File f = new File("E:/abc/ab/a");
        f.mkdirs();
    }
}

3. 获取相对路径getPath()和绝对路径getAbsolutePath()，文件名getName()和文件大小length()。

package xyz.liangshuai.demo1;

import java.io.File;

public class Test3 {

    public static void main(String[] args) {
        File f = new File("abc.txt");
        
        System.out.println(f.getPath());
        System.out.println(f.getAbsolutePath());
        System.out.println(f.getName());
        System.out.println(f.length());
    }
}

4. IO流

   
   
   IO流.png

5. 输入流

package xyz.liangshuai.demo1;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

public class Test4 {

    public static void main(String[] args) {
        FileInputStream fis = null;
        try {
            //创建输入流的对象
            fis = new FileInputStream("stu.txt");
            int b = 0;
            while ((b = fis.read()) != -1) {
                System.out.print((char)b);
            }
            
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                fis.close();//关闭流，释放资源
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

5. 复制文件

package xyz.liangshuai.demo1;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class TestCopy {

    public static void main(String[] args) {
        FileInputStream fis = null;
        FileOutputStream fos = null;
        
        try {
            fis = new FileInputStream("photo.jpg");
            fos = new FileOutputStream("photo1.jpg");
            int b = 0;
            while ((b = fis.read()) != -1) {
                fos.write(b);
            }
            
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                fis.close();
                fos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

6. 输出流

package xyz.liangshuai.demo1;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class Test6 {

    public static void main(String[] args) {
        FileOutputStream fos = null;
        try {
            //true追加内容，false覆盖
            fos = new FileOutputStream("qwe.txt",true);
            String s = "啦啦啦";
            fos.write(s.getBytes());//写入数据
            
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                fos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}