代码运行截图

1.

import org.testng.annotations.Test;

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

public class createFile {
    public static void main(String[] args) {

    }
    //方法1
    @Test
    public void create01(){

        String pathname ="D://陈志烨20215220608文件一.txt";

        File file = new File(pathname);

        try {
            file.createNewFile();
            System.out.println("创建文件一成功");
        } catch (IOException e) {
            throw new RuntimeException(e);
        }


    }
    @Test
    //方法二
    public void create02(){
//        String pathname="D://";
        File parentFile=new File("D://");

        String fileName="陈志烨20215220608文件二.txt";

        File file=new File(parentFile,fileName);

        try {
            file.createNewFile();
            System.out.println("创建文件二成功");
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    @Test
    public void create03(){
        String parentPath="D://";
        String filePath="陈志烨20215220608文件三.txt";

        File file=new File(parentPath,filePath);

        try {
            file.createNewFile();
            System.out.println("创建文件三成功");
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }


}

 2.

import org.testng.annotations.Test;

import java.io.File;

public class FileInformation {
    public static void main(String[] args) {

    }
    //获取文件信息
    @Test
    public void Info(){
        //先创建文件对象
        File file=new File("D://陈志烨20215220608文件一.txt");

        //调用相应方法，得到对应信息
        System.out.println("文件名称:"+file.getName());

        System.out.println("文件绝对路径:"+file.getAbsolutePath());

        System.out.println("文件父目录:"+file.getParent());

        System.out.println("文件大小（字节）"+file.length());

        System.out.println("文件是否存在:"+file.exists());

        System.out.println("是否是文件:"+file.isFile());

        System.out.println("是否是目录:"+file.isDirectory());
    }

}

3.

import org.testng.annotations.Test;

import java.io.File;

public class fileDirectory {
    public static void main(String[] args) {

    }
    @Test
    //删除文件
    public void fileDelete(){
        String filePath="D://陈志烨20215220608文件一.txt";
        File file=new File(filePath);
        if (file.exists()){
            if (file.delete()){
                System.out.println(filePath+"删除成功");
            }else {
                System.out.println(filePath+"删除失败");
            }
        }else {
            System.out.println("文件不存在");
        }
    }
    //输出目录
    @Test
    public void fileDeleteD(){
        String filePath="D://陈志烨20215220608.txt";
        File file=new File(filePath);
        if (file.exists()){
            if (file.delete()){
                System.out.println(filePath+"删除成功");
            }else {
                System.out.println(filePath+"删除失败");
            }
        }else {
            System.out.println("目录不存在");
        }


    }

    //判断目录是否存在，不存在就创建
    @Test
    public void fileDeleteD1(){
        String dirPath="D://text//陈志烨20215220608dir1.txt";
        File file=new File(dirPath);
        if (file.exists()){
            System.out.println(dirPath+"该目录已经存在");
        }else {
            if (file.mkdir()){
                System.out.println("创建成功");
            }else {
                System.out.println("创建失败");
            }
        }
    }

}

4.

import java.util.Scanner;

public class scanPrintTest {
    public static void main(String[] args) {
        //创建Scanner对象，接受从控制台输入
        Scanner input =new Scanner(System.in);
        //接受String类型
        String str =input.next();
        //输出结果
        System.out.println(str);

        System.out.println("hellow world");
    }
}

import java.util.Scanner;

public class scanTest {
    public static void main(String[] args) {
        Scanner input=new Scanner(System.in);
        //double类型的数据
        System.out.println("请输入一个double类型的数");
        double d=input.nextDouble();
        System.out.println(d);
        //int类型的数据
        System.out.println("请输入一个int类型的数");
        int i=input.nextInt();
        System.out.println(i);
        //字符串类型的数据
        System.out.println("请输入一个string类型的数");
        String s=input.next();
        System.out.println(s);


    }
}

 5.

import org.testng.annotations.Test;

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

public class fileInputStream {
    public static void main(String[] args) {

    }
    @Test
    public void fileIn1(){
        String filePath="D://陈志烨20215220608file.txt";
        int readData;
        FileInputStream fileInputStream=null;

        try {
            //创建FileInputStream对象，用于读取文件
            fileInputStream=new FileInputStream(filePath);

            while ((readData=fileInputStream.read())!=-1){
                System.out.println((char)readData);
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }finally {
            //关闭文件流
            try {
                fileInputStream.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }
    @Test
    public void fileIn2(){
        String filePath="D://陈志烨20215220608file.txt";
        int readData;
        int readlength=0;
        //字节数组
        byte[] buf =new byte[8];
        FileInputStream fileInputStream=null;
        try {
            //创建FileInputStream对象，用于读取文件
            fileInputStream=new FileInputStream(filePath);

            while ((readlength=fileInputStream.read(buf))!=-1){
                System.out.println(new String(buf,0,readlength));
            }

        } catch (IOException e) {
            throw new RuntimeException(e);
        }finally {
            //关闭文件流
            try {
                fileInputStream.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }
    @Test
    public void fileIn3(){
        String filePath="D://陈志烨20215220608file.txt";
        int readData;
        int readlength=0;
        //字节数组
        byte[] buf =new byte[8];
        FileInputStream fileInputStream=null;
        try {
            //创建FileInputStream对象，用于读取文件
            fileInputStream=new FileInputStream(filePath);
            while ((readlength=fileInputStream.read(buf))!=-1){
                System.out.println(new String(buf,0,readlength));
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }finally {
            //关闭文件流
            try {
                fileInputStream.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }

    }

}

6.

import org.testng.annotations.Test;

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

public class outputStream {
    public static void main(String[] args) {

    }
    //使用FileOutputStream将数据写到文件中
    //如果文件不存在，则创建文件
    @Test
    public void writeFile(){
        String filePath="D://陈志烨20215220608fileout.txt";
        //创建对象
        FileOutputStream fileOutputStream=null;
        try {
            fileOutputStream=new FileOutputStream(filePath);

            //写入一个字节
            //fileOutputStream.write('H');

            //写入一个字符串
//            String str="hello socket";
//            str.getBytes()//将字符串转换为字节数组
//            fileOutputStream.write(str.getBytes());

            //写入字符串
            String str ="hello lst";
            fileOutputStream.write(str.getBytes(),0,str.length());

        } catch (IOException e) {
            throw new RuntimeException(e);
        }finally {
            try {
                fileOutputStream.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }
}

7.

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

public class copyPic {
    //file读和写实现复制文件
    public static void main(String[] args)throws Exception {
        //创建file对象
        File f=new File("D://test.jpg");
        //判断文件是否存在
        if (f.exists()){
            System.out.println("test.jpg存在，可以复制");
        }else {
            f.createNewFile();
            System.out.println("test.jpg不存在，新建成功，可以复制");
        }
        //创建FileInputStream对象
        FileInputStream inp=new FileInputStream(f);


        File f1=new File("d://demo");
        if (f1.isDirectory()){
            FileOutputStream out=new FileOutputStream("d://demo//"+f.getName());
            byte bytes[]=new byte[1024];
            int temp=0;
            while ((temp=inp.read(bytes))!=-1){
                out.write(bytes,0,temp);
            }
            //结束
            inp.close();
            out.close();
            System.out.println("文件拷贝成功");
        }else {
            f1.mkdir();
            System.out.println("demo目录不存在，已经创建成功，继续复制");
            FileOutputStream out=new FileOutputStream(":d://demo//"+f.getName());
            byte bytes[]=new byte[1024];
            int temp=0;
            while ((temp=inp.read(bytes))!=-1){
                out.write(bytes,0,temp);
            }
            //结束
            inp.close();
            out.close();
            System.out.println("文件拷贝成功");


        }

    }
}

原文地址：http://www.cnblogs.com/chenzhiye1845/p/16859235.html