目录

分类

字节流

InputStream

OutputStream

文件拷贝

字符流

FileReader

FileWriter

处理流

BufferedReader

BufferedWriter

文本拷贝

        流是从起源到接受的有序数据，通过流的方式允许程序使用相同的方式来访问不同的输入/输出源。        

分类

按数据单位分：字节流(二进制文件)        字符流(文本文件）

按数据流向分：输入流        输出流

按流的角色分：节点流        处理流 

IO流的40多个类都是由这四个抽象基类派生的

字节流

InputStream

常用子类：

1. FileInputStream        文件输入流
2. BufferedInputStream          缓冲字节输入流
3. ObjectInputStream        对象字节输入流             

import java.io.FileInputStream;public class FileInputStream_ {public static void main(String[] args) {readFile01();System.out.println();readFile02();}public static void readFile01(){String path="D:\\\\javacode\\\\IO\\\\src\\\\test.txt";int read;FileInputStream fis=null;try {fis=new FileInputStream(path);while((read=fis.read())!=-1)//读取一个字节的数据，读到末尾返回-1{System.out.print((char)read);//一个一个读}} catch (Exception e) {e.printStackTrace();}finally {try {fis.close();} catch (Exception e) {e.printStackTrace();}}}public static void readFile02(){String path="D:\\\\javacode\\\\IO\\\\src\\\\test.txt";byte[] buf=new byte[8];FileInputStream fis=null;int len;try {fis=new FileInputStream(path);while((len=fis.read(buf))!=-1)//读取一个字节的数据，读到末尾返回-1{System.out.print((new String(buf,0,len)));//一次最多读入buf.length字节的数据，存入字节数组buf}} catch (Exception e) {e.printStackTrace();}finally {try {fis.close();} catch (Exception e) {e.printStackTrace();}}}
}

OutputStream

子类：FileOutputStream

import java.io.FileOutputStream;public class FileOutputStream_ {public static void main(String[] args) {writeFile01();}public static void writeFile01(){String path="D:\\\\javacode\\\\IO\\\\src\\\\test.txt";FileOutputStream fos=null;try {//fos=new FileOutputStream(path);//覆写fos=new FileOutputStream(path,true);//加true,追加文本fos.write('6');fos.write("helloworld".getBytes());//获取str对应的字节数组} catch (Exception e) {e.printStackTrace();}finally {try {fos.close();} catch (Exception e) {e.printStackTrace();}}}
}

#字节流中文会乱码，这是因为只能存一个字节一个字节输出 

文件拷贝

import java.io.FileInputStream;
import java.io.FileOutputStream;public class FileCopy {public static void main(String[] args) {//文件拷贝FileInputStream fileInputStream=null;//输入流FileOutputStream fileOutputStream=null;//输出流//源文件和目标文件String srcpath="C:\\\\Users\\\\Elysia\\\\Pictures\\\\Saved Pictures\\\\illust_86465238_20210124_003335.jpg";String destpath="D:\\\\javacode\\\\IO\\\\src\\\\pic.jpg";try {fileOutputStream=new FileOutputStream(destpath,true);fileInputStream=new FileInputStream(srcpath);byte[] buf=new byte[1024];int len;while((len=fileInputStream.read(buf))!=-1){fileOutputStream.write(buf,0,len);}} catch (Exception e) {e.printStackTrace();}finally {try {fileOutputStream.close();fileInputStream.close();}catch (Exception e){e.printStackTrace();}}}
}

字符流

FileReader

import java.io.FileReader;public class FileReader_ {public static void main(String[] args) {FileReader fileReader=null;String path="D:\\\\javacode\\\\IO\\\\src\\\\test.txt";try {fileReader=new FileReader(path);char[] buf=new char[8];//用char接收int len;while((len=fileReader.read(buf))!=-1){System.out.print(new String(buf,0,len));}
//            int read;//单个读取
//            while((read= fileReader.read())!=-1){
//                System.out.print((char)read);
//            }} catch (Exception e) {e.printStackTrace();}finally {try {fileReader.close();//关闭文件}catch (Exception e){e.printStackTrace();}}}
}

FileWriter

import java.io.FileWriter;public class FileWriter_ {public static void main(String[] args) {FileWriter fileWriter=null;String path="D:\\\\javacode\\\\IO\\\\src\\\\test.txt";try{fileWriter=new FileWriter(path,true);//加true表示追加fileWriter.write("\\n成功写入");}catch (Exception e){e.printStackTrace();}finally {try{fileWriter.close();//必须 一定 关闭流，才能真正的写入}catch (Exception e){e.printStackTrace();}}}
}

必须 一定 关闭/flush流，才能真正的写入

处理流

        将“流”包装，在其之上为程序提供更强大的读写功能

 节点流的数据源是特定的，而处理流则利用了向上转型，可以封装多种“流”，减小了节点流之间的差异。

优势：

1. 使用处理流进行 读写操作更简单
2. 处理流增加了缓冲，提高效率 

#在关闭包装流的时候，会自动关闭里面封装的字节流

BufferedReader

        从字符输入流读取文本，缓冲字符，以提供字符，数组和行的高效读取。

import java.io.BufferedReader;
import java.io.FileReader;public class BufferedReader_ {public static void main(String[] args) throws Exception{String path="D:\\\\javacode\\\\IO\\\\src\\\\test.txt";BufferedReader bufferedReader=new BufferedReader(new FileReader(path));String line;//按行读取，效率高while((line=bufferedReader.readLine())!=null){System.out.println(line);//读取一行}bufferedReader.close();//只需要关闭包装流}
}

BufferedWriter

        文本写入字符输出流，缓冲字符，以提供单个字符，数组和字符串的高效写入。

import java.io.BufferedWriter;
import java.io.FileWriter;public class BufferedWriter_ {public static void main(String[] args) throws Exception{String path="D:\\\\javacode\\\\IO\\\\src\\\\test.txt";BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter(path,true));bufferedWriter.newLine();//插入一个换行bufferedWriter.write("成功写入");bufferedWriter.close();}
}

文本拷贝

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;public class TxtCopy {public static void main(String[] args) throws Exception{String dest="D:\\\\javacode\\\\IO\\\\src\\\\dest.txt";String src="D:\\\\javacode\\\\IO\\\\src\\\\test.txt";BufferedReader bufferedReader=new BufferedReader(new FileReader(src));BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter(dest));String line;while((line=bufferedReader.readLine())!=null){bufferedWriter.write(line);//末尾没有换行符bufferedWriter.newLine();//每读取一行，插入换行符}bufferedWriter.close();bufferedReader.close();}
}