io

字节输入流:FileInputStream  FilterInputStream BufferedInputStream
字节输出流:FileOutputStream FilterOutputStream  BufferedOutputStream 
字符输入流：Reader BufferedReader inputStreamReader FileReader
字符输出流：Write  BufferedWriter outputStreamWriter  FileWriter
OutputStreamWriter  字符流转换成字节流
InputStreamReader: 字节流转化成字符流
字节打印流 PrintStream

1. 创建文件，遍历文件夹，转换时间

import java.io.File;
import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class file {

    public static void main(String[] args){
        File file = new File("F:/学习");
        if(!file.exists()){
            try {
                file.createNewFile();
                System.out.printf("文件创建成功");
                File[] names = file.listFiles();
                for (File f:names){
                    System.out.printf(""+f.getName());
                    System.out.println("最后修改时间"+f.lastModified());
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        File file2 = new File("F:/学习/my");
        File[] names = file2.listFiles();
        for (File f:names) {
            System.out.println(f.getName());
            System.out.println(f.lastModified());
            Date date = new Date(f.lastModified());
            DateFormat df = new SimpleDateFormat("HH:mm:ss");
            System.out.println(""+df);
            System.out.println(df.format(date));
            System.out.println("-------");
        }
    }
}

2. 遍历文件，输出其中的jpg，并打印图片的绝对路径

import java.io.File;

public class file {

    public static void main(String[] args){
        
        findFile( new File(" "),".jpg");

    }

    private static void findFile(File target,String ext){
        if(target == null)
            return;
        if(target.isDirectory()){
            File[] files = target.listFiles();
            if(files != null){
                for (File f:files) {
                    findFile(f,ext);
                }
            }
        }else{
            String name = target.getName().toLowerCase();
            if(name.endsWith(ext)){
                System.out.println(target.getAbsolutePath());
            }
        }
    }

}

 3.文件的写入写出针对的是程序

　　输出内容到文件

import java.io.*;

public class file {

    public static void main(String[] args){
            out();
    }

    private static void out(){
        File file = new File("F:\学习\1.txt");
        try {
            OutputStream out = new FileOutputStream(file);
            String info ="I love java";
            out.write(info.getBytes());
            out.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

 4.写入文件内容到程序 

import java.io.*;

public class file {

    public static void main(String[] args){
        in();
    }

    private static void in(){
        File file = new File("F:\学习\1.txt");
        try {
            InputStream in = new FileInputStream(file);
            byte[] bytes = new byte[1024];
            StringBuffer buffer = new StringBuffer();
            int len = -1;
            while ((len = in.read(bytes)) != -1){
                buffer.append(new String(bytes,0,len));
            }
            System.out.println(buffer);
            in.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

 5. 字符流

写入字符到文件

import java.io.*;

public class file {

    public static void main(String[] args){
        in();
    }

    private static void in(){
        File file = new File("F:\学习\1.txt");

        try {
            Writer in = new FileWriter(file,true);
            in.write("I hate you");
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

从文件读出字符

import java.io.*;

public class file {

    public static void main(String[] args){
        in();
    }

    private static void in(){
        File file = new File("F:\学习\1.txt");

        try {
            Reader in = new FileReader(file);
            char[] chars = new char[1];
            int len = -1;
            StringBuffer stringBuffer = new StringBuffer();
            while ((len = in.read(chars)) != -1){
                stringBuffer.append(chars,0,len);
            }
            System.out.printf(""+stringBuffer);
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

 6. OutputStreamWriter  字符流转换成字节流

import java.io.*;
import java.nio.charset.Charset;

public class file {

    public static void main(String[] args) throws FileNotFoundException {
        InputStream inputStream = new FileInputStream("F:\学习\1.txt");
        in(inputStream);
    }

    private static void in(InputStream inputStream){
        Reader reader = new InputStreamReader(inputStream, Charset.defaultCharset());
        char[] chars = new char[1024];
        int len = -1;
        try {
            while ((len = reader.read(chars)) != -1){
                System.out.println(new String(chars,0,len));
            }
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

　InputStreamReader: 字节流转化成字符流

import java.io.*;
import java.nio.charset.Charset;

public class file {

    public static void main(String[] args) throws FileNotFoundException {
      OutputStream outputStream = new  FileOutputStream("F:\学习\1.txt");
      out(outputStream);

    }
    private static void out(OutputStream outputStream){
        Writer writer = new OutputStreamWriter(outputStream,Charset.defaultCharset());
        try {
            writer.write("lllll");
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

 7. BufferedOutputStream 

import java.io.*;

public class file {

    public static void main(String[] args) throws FileNotFoundException {
        out();
    }
    private static void out(){
            File file = new File("F:/学习/1.txt");
        try {
            OutputStream outputStream = new FileOutputStream(file);
            BufferedOutputStream bos = new BufferedOutputStream(outputStream);
            String info = "mmmmm";
            bos.write(info.getBytes());
            bos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.io.*;

public class file {

    public static void main(String[] args) throws FileNotFoundException {
        in();
    }
    private static void in(){
            File file = new File("F:/学习/1.txt");
        try {
            InputStream inputStream = new FileInputStream(file);
            BufferedInputStream bis = new BufferedInputStream(inputStream);
            byte[] bytes = new byte[1024];
            int len = -1;
            while((len = bis.read(bytes)) != -1){
                System.out.println(new String(bytes,0,len));
            }
            bis.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

 字节打印流 PrintStream

import java.io.*;

public class file {

    public static void main(String[] args) throws FileNotFoundException {
        in();
    }
    private static void in(){
        try {
            File file = new File("F:/学习/1.txt");
            OutputStream outputStream = new FileOutputStream(file);
            BufferedOutputStream out = new BufferedOutputStream(outputStream);
            PrintStream printStream = new PrintStream(out);
            printStream.println("啦啦啦");
            printStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

import java.io.*;

public class file {

    public static void main(String[] args) throws FileNotFoundException {
        in();
    }
    private static void in(){
        try {
            File file = new File("F:/学习/1.txt");
            Writer writer = new FileWriter(file);
            BufferedWriter bufferedWriter = new BufferedWriter(writer);
            PrintWriter printWriter = new PrintWriter(bufferedWriter);
            printWriter.println("wwww");
            printWriter.flush();
            printWriter.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}