IO

2022-08-06 22:04:09 阅读：161 来源： 互联网

标签：IO read mayikt System File new public

File类

package IO;

import java.io.File;

/**
 *
 **/
public class Test01 {
    public static void main(String[] args) {
        /**
         * java.io包
         * io对磁盘进行操作 文件操作（增删改查）
         */
        File file = new File("E:/mayikt/mayikt.txt");
        System.out.println(file);//E:\mayikt\mayikt.txt
        //"E:/mayikt/mayikt.txt"
        File file1=new File("E:/mayikt/","mayikt.txt");
        System.out.println(file1);//E:\mayikt\mayikt.txt
        File file2=new File("E:/mayikt/");
        File file3=new File(file2,"mayikt.txt");
        System.out.println(file3);//E:\mayikt\mayikt.txt
    }
}

File类创建功能

package IO;

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

/**
 *
 **/
public class Test02 {
    public static void main(String[] args) throws IOException {
        /**
         * 在E:\mayikt创建mayikt.txt
         */
        File file = new File("E:/mayikt.txt");
        boolean newFile = file.createNewFile();//不能越级创建，如果E:/mayikt/mayikt.txt，没有mayikt这个文件夹，就会失败
        System.out.println(newFile);
        /**
         * mkdir
         */
        File file2 = new File("E:/mayikt");
        boolean mkdir = file2.mkdir();//不能跨级，创建文件夹，不能重复创建
        System.out.println(mkdir);
        File file3 = new File("E:/mayikt/mayikt2");//可以越级创建
        System.out.println(file3.mkdirs());

    }
}

File类判断方法

package IO;

import java.io.File;

/**
 *
 **/
public class Test03 {
    public static void main(String[] args) {
        File file = new File("E:/mayikt.txt");
        if(file.isFile()){
            System.out.println("是文件");
        }else{
            System.out.println("不是文件");
        }
        File file2 = new File("E:/mayikt");
        if(file.isDirectory()){
            System.out.println("是文件夹");
        }else{
            System.out.println("不是文件夹");
        }
        File file3 = new File("E:/mayikt");
        if(file.exists()){
            System.out.println("已经创建");
        }else{
            System.out.println("没有创建");
        }
    }
}

File类常见获取方法

package IO;

import java.io.File;

/**
 *
 **/
public class Test04 {
    public static void main(String[] args) {
        File file = new File("E:/mayikt/");
        System.out.println(file.getAbsolutePath());//E:\mayikt 绝对路径
        System.out.println(file.getPath());//E:\mayikt 抽象路径-->相对路径
        System.out.println(file.getName());//mayikt 文件夹名
        String[] list = file.list();//返回目录下所有文件和文件夹，String类型
        for (String s :
                list) {
            System.out.println(s);
        }
        File[] files = file.listFiles();
        for (File f :
                files) {
            System.out.println(f);//E:\mayikt\mayikt2 返回目录下所有文件和文件夹,以File类型
        }
    }
}

File删除

package IO;

import java.io.File;

/**
 *
 **/
public class Test05 {
    public static void main(String[] args) {
        File file = new File("E:/mayikt/");
        boolean delete = file.delete();
        System.out.println(delete);//false,因为E:/mayikt/下还有文件，删除目录的化需要删除里面的文件或者目录
        File file2 = new File("E:/mayikt.txt");
        System.out.println(file2.delete());//true   删除文件，直接删除
    }
}

循环删除

递归求阶乘（注意栈溢出）

方法定义中调用方法本身

package IO;

/**
 *
 **/
public class Test06 {
    public static void main(String[] args) {
        jc(5);
    }
    public static int jc(int n){
        if(n==1){
            return 1;
        }else{
            return n*jc(n-1);
        }
    }
}

I/O流

input输入：硬盘读取到内存

output输出：写到硬盘

流的分类

按流向：输入流和输出流

按类型：字节流，字符型

推荐使用：

纯文本用字符

图片音频：字节流

字节输出流

写数据到磁盘

package IO;

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

/**
 *初次使用
 **/
public class Test07 {
    public static void main(String[] args) throws IOException {
        FileOutputStream fileOutputStream = new FileOutputStream("E:/mayikt.txt");
        fileOutputStream.write(97);
        fileOutputStream.write(98);
        fileOutputStream.write(99);
        fileOutputStream.write(100);
        fileOutputStream.close();
           /**
         * write(byte[])
         */
        byte[] a={97,98,99,100};
        fileOutputStream.write(a);
        fileOutputStream.close();
    }
}

字节流换行追加写

package IO;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;

/**
 *
 **/
public class Test08 {
    public static void main(String[] args) throws IOException {
        File file = new File("E:/mayikt.txt");
        //true为追加
        FileOutputStream fileOutputStream = new FileOutputStream(file,true);
        String str="我是蔡23123徐坤";
        for (int i = 0; i < 10; i++) {
            fileOutputStream.write(str.getBytes());
            //换行
            fileOutputStream.write("\n".getBytes());
        }


    }
}

字节流读取

package IO;

import java.io.*;

/**
 *
 **/
public class Test09 {
    public static void main(String[] args) throws IOException {
        File file = new File("E:/mayikt.txt");
        //true为追加
        FileInputStream fileInputStream = new FileInputStream(file);

        InputStreamReader inputStreamReader=new InputStreamReader(fileInputStream,"utf-8");
        try{
            //read()一个一个读取
            int read = inputStreamReader.read();
            while(read!=-1){
                System.out.print((char)read);
                read=inputStreamReader.read();
            }
            System.out.println((char)read);
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if(fileInputStream!=null){
                try{
                    fileInputStream.close();
                }catch (Exception e){
                    e.printStackTrace();
                }

            }
        }

    }
}

优化

package IO;

import java.io.*;

/**
 *
 **/
public class Test09 {
    public static void main(String[] args) throws IOException {
        File file = new File("E:/mayikt.txt");
        //true为追加
        FileInputStream fileInputStream = new FileInputStream(file);

        InputStreamReader inputStreamReader=new InputStreamReader(fileInputStream,"utf-8");
        try{
            //read()一个一个读取
            int read ;
            while((read=inputStreamReader.read())!=-1){
                System.out.print((char)read);
//                read=inputStreamReader.read();
            }
            System.out.println((char)read);
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if(fileInputStream!=null){
                try{
                    fileInputStream.close();
                }catch (Exception e){
                    e.printStackTrace();
                }

            }
        }

    }
}

字节流拷贝

package IO;

import java.io.*;

/**
 * 字节流拷贝
 **/
public class Test10 {
    public static void main(String[] args) throws IOException {
        FileInputStream fileInputStream=new FileInputStream(new File("E:/mayikt.txt"));
        FileOutputStream fileOutputStream = new FileOutputStream(new File("E:/mayikt2.txt"));
        int read;
        while((read=fileInputStream.read())!=-1){
            fileOutputStream.write(read);
        }
        fileOutputStream.close();
        fileInputStream.close();
    }
}

1024数组读取

package IO;

import java.io.*;

/**
 * 字节流拷贝
 **/
public class Test10 {
    public static void main(String[] args) throws IOException {
        FileInputStream fileInputStream=new FileInputStream(new File("E:/mayikt.txt"));
        FileOutputStream fileOutputStream = new FileOutputStream(new File("E:/mayikt2.txt"));
        byte[] bytes = new byte[1024];
        int read;
        while((read=fileInputStream.read(bytes))!=-1){
            System.out.println(read);
            System.out.println(new String(bytes,0,read));
        }
        fileOutputStream.close();
        fileInputStream.close();
    }
}

字节缓冲流

减少系统调用（用户态到内核调用，效率很低）

字节缓冲流默认大小8k

package IO;

import java.io.*;

/**
 * 利用缓冲流写入数据
 **/
public class Test11 {
    public static void main(String[] args) throws IOException {
            FileOutputStream fileOutputStream=new FileOutputStream(new File("E:/mayikt.txt"));
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(fileOutputStream);
        bufferedOutputStream.write("jdjadkhadiu".getBytes());
        bufferedOutputStream.close();
        fileOutputStream.close();
    }
}

输出缓冲一样

复制时，都是用缓冲流进行操作

汉字占用字节

汉字GBK占两个字节

汉字UTF-8占用3个字节

编码乱码

package IO;

import java.io.*;

/**
 * 利用缓冲流写入数据
 **/
public class Test11 {
    public static void main(String[] args) throws IOException {
        FileInputStream fileInputStream=new FileInputStream(new File("E:/mayikt.txt"));
        BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream);

        byte[] bytes = new byte[1024];
        int read;
        while((read=bufferedInputStream.read(bytes))!=-1){
            System.out.println(read);
            System.out.println(new String(bytes,0,read,"GBK"));//鏄紑鍙戝紑鍙戜簡瀹㈡湇缁忕悊j //文件内容为utf-8
        }
        bufferedInputStream.close();
        fileInputStream.close();
    }
}

存是编码，读是解码

字符流

写

package IO;

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

/**
 *字符流写
 **/
public class Test12 {
    public static void main(String[] args) throws IOException {
        FileOutputStream fileOutputStream = new FileOutputStream("E:/mykt.txt");
        OutputStreamWriter outputStreamWriter = new OutputStreamWriter(fileOutputStream,"Utf-8");
        outputStreamWriter.write("中国万岁da");
        outputStreamWriter.close();
        fileOutputStream.close();
    }
}

package IO;

import java.io.*;
import java.util.Arrays;

/**
 * 字符流读取
 **/
public class Test13 {
    public static void main(String[] args) throws IOException {
        FileInputStream fileInputStream = new FileInputStream("E:/mykt.txt");
        InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream,"UTF-8");
        char[] chars=new char[1024];
        int len;
        while ((len=inputStreamReader.read(chars))!=-1){
            System.out.println(new String(chars,0,len));
        }

    }
}

转换流便捷形式

FileWrite和FileOut

package IO;

import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

/**
 *字符转换流
 **/
public class Test14 {
    public static void main(String[] args) throws IOException {
        FileWriter fileWriter = new FileWriter("E:/mykt.txt", true);
        fileWriter.write("ufhiahfaikfajfaf");
        fileWriter.close();
        FileReader fileReader = new FileReader("E:/mykt.txt");
        char[] chars=new char[1024];
        int len;
        while((len=fileReader.read(chars))!=-1){
            System.out.println(new String(chars,0,len));
        }
    }
}
无法指定编码，需要指定编码使用字符流，字符流需要追加文件里买的字节流加上true

字符缓冲流

package IO;

import java.io.*;

/**
 *字符转换流+缓冲流
 **/
public class Test14 {
    public static void main(String[] args) throws IOException {
        FileWriter fileWriter = new FileWriter("E:/mykt.txt", true);
        BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
        bufferedWriter.write("ufhiahfaikfajfaf");
        bufferedWriter.newLine();//换行
        bufferedWriter.close();
        fileWriter.close();
        FileReader fileReader = new FileReader("E:/mykt.txt");
        BufferedReader bufferedReader = new BufferedReader(fileReader);
        
        String str;
        while((str=bufferedReader.readLine())!=null){
            //System.out.println(bufferedReader.readLine());//不能这样写，因为每执行一次其实就是往下走了，我们需要一个变量来接收
            System.out.println(str);
        }

    }
}

标签：IO,read,mayikt,System,File,new,public
来源： https://www.cnblogs.com/yhdxx/p/16557983.html

本站声明： 1. iCode9 技术分享网（下文简称本站）提供的所有内容，仅供技术学习、探讨和分享；
2. 关于本站的所有留言、评论、转载及引用，纯属内容发起人的个人观点，与本站观点和立场无关；
3. 关于本站的所有言论和文字，纯属内容发起人的个人观点，与本站观点和立场无关；
4. 本站文章均是网友提供，不完全保证技术分享内容的完整性、准确性、时效性、风险性和版权归属；如您发现该文章侵犯了您的权益，可联系我们第一时间进行删除；
5. 本站为非盈利性的个人网站，所有内容不会用来进行牟利，也不会利用任何形式的广告来间接获益，纯粹是为了广大技术爱好者提供技术内容和技术思想的分享性交流网站。

ICode9

IO