javaIo流笔记

一、文件创建

import org.junit.Test;

import java.io.File;
import java.io.IOException;
public class FileCreate {
    public static void main(String[] args) {
    }
    @Test
    public void create1()
    {
        String filePath = "D:\\file1.txt";
        File file = new File(filePath);
        try{
            file.createNewFile();
            System.out.println("创建文件1成功");
        }catch (IOException e){
            e.printStackTrace();
        }
    }
    @Test
    public void create2()
    {
        File parentFile = new File("D:\\file2.txt");
        String fileName = "file2.txt";
        File file = new File(parentFile, fileName);
        try{
            file.createNewFile();
            System.out.println("创建文件2成功");
        }catch (IOException e){
            e.printStackTrace();
        }
    }
    @Test
    public void create3()
    {
        String parentPath = "D:\\file3.txt";
        String filePath = "file3.txt";
        File file = new File(parentPath, filePath);
        try{
            file.createNewFile();
            System.out.println("创建文件3成功");
        }catch (IOException e){
            e.printStackTrace();
        }
    }

二、获取文件的相关信息

import org.junit.Test;

import java.io.File;

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

    }
    @Test
    public void Info(){
        //先创建文件对象
        File file = new File("D:\\file1.txt");
        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());
    }
}

三、目录的操作

import org.junit.Test;

import java.io.File;

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

    }

    //删除文件
    @Test
    public void fileDelete()
    {
        String filePath = "D:\\file1.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");
        }
    }


    //删除目录
    @Test
    public void fileDeleteD()
    {
        String filePath = "D:\\file1.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:\\file1.txt";
        File file = new File(dirPath);

        if(file.exists()){
            System.out.println(dirPath + "该目录已经存在");
        }else{
            if(file.mkdirs()){
                System.out.println("创建成功");
            }else{
                System.out.println("创建失败");
            }
        }
    }
}

四、Scanner与Println

基本键盘输入：

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("hello world");
    }
}

常见键盘输入类型： 

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.print("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.print("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.print("请输入string类型的数:");
        String s = input.next();
        System.out.println(s);
    }
}