java--IO

package Demo;
import java.io.*;
public class JavaIO {
    public static void main(String[] args){
        try {
            //文件IO，File对象既可以表示文件，也可以表示目录
            File f1 = new File("C:\Users\shun.guo\Desktop\Java\javatest\test.txt");
            System.out.println(f1);
            File f2 = new File("C:\Users\shun.guo\Desktop\Java\javatest");
            System.out.println(f1.isDirectory());//false
            System.out.println(f1.isFile());//true
            System.out.println(f2.isDirectory());//true
            System.out.println(f2.isFile());//false

            //creat file
            File creatfile1 = new File("C:\Users\shun.guo\Desktop\Java\javatest2");
            File creatfile2 = new File("C:\Users\shun.guo\Desktop\Java\javatest\test2.txt");
            if (!creatfile1.exists()) {
                System.out.println("不存在目录,开始创建这个目录路径");
                creatfile1.mkdir();//创建目录
            }else{
                System.out.println("目录已经存在");
            }
            if (!creatfile2.exists()) {
                System.out.println("不存在文件,开始创建文件");
                creatfile2.createNewFile();//创建文件
            }else {
                System.out.println("文件已经存在");
            }

            //listdir
            File f4 = new File("C:\Users\shun.guo\Desktop\Java\javatest");
            File[] f4listdir =  f4.listFiles();
            System.out.println("列出路径"+f4+"下的所有文件");
            for (File j : f4listdir){
                System.out.println(j);
            }


        }catch (Exception e){//IO操作的时候必须捕获异常
            System.out.println("异常");
            e.printStackTrace();
        }
    }
}

package Demo;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

public class JavaIoInputstream {
    public static void readFile(){
        try{
            InputStream input = new FileInputStream("D:\Uesrs\shun.guo\Desktop\Java\javatest\test2.txt");
            for (;;){
                int n = input.read();
                if (n == -1){
                    break;
                }
                System.out.println(n);
            }
            input.close();
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    public static void main(String[] args){
        JavaIoInputstream.readFile();
    }
}

package Demo;

import java.io.*;

public class readtxt {
    //java read txt
    public static void main(String[] args) throws IOException{
        String filename="C:\Users\shun.guo\Desktop\Java\javatest\test2.txt";
        FileReader reader = new FileReader(filename);
        BufferedReader buffreader = new BufferedReader(reader);//使用Bufferreader封装filereader
        String line = buffreader.readLine();
        while (line != null){
            System.out.println(line);
            line=buffreader.readLine();//bufferreader读取到最后一行会返回null
        }
        buffreader.close();
        reader.close();
    }
}