目录

IO

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常用的流

流根据方向可以分为输入流和输出流（相对内存而言），输入流也叫Read(读),输出流也叫Writer(写)

流根据类型分为字节流和字符流，前者一次1读取一个字节，后者一次读取两个字节

• FileInputStream

• FileOutputStream

• FileReader

• FileWriter

• BufferedInputStream

• BufferedOutputStream

• BufferedReader

• BufferedWriter

• InputStreamReader

• OutputStreamWriter

• ObjectInputStream

• ObjectOutputStream

• DataInputStream

• DataOutputStream

• PrintStream

• PrintWriter

FileInputStream

文件字节输入流 将计算机硬盘中的内容写到内存中

int read()

文件temp.txt的内容为abcdefg 注意不要换行

package io;
import java.io.FileInputStream;
import java.io.IOException;
public class ByteStream {public static void main(String[] args) {FileInputStream fis = null;try {String filePath = "src/io/temp.txt";//可以是相对路径，也可以是绝对路径fis = new FileInputStream(filePath);int temp;while ((temp = fis.read()) != -1){System.out.println(temp); }} catch (IOException e){e.printStackTrace();} finally {try {if(fis != null){fis.close();}}catch (IOException e){e.printStackTrace();}}}
}

int read(byte[] bytes)

读取数据之前在内存中准备一个字节数组，一次读取多个字节存入字节数组中，效率高。返回每次读取到数据的字节长度

package io;
import java.io.FileInputStream;
import java.io.IOException;
public class ByteStream {public static void main(String[] args) throws IOException {String filePath = "src/io/temp.txt";FileInputStream fis = new FileInputStream(filePath);byte[] bytes = new byte[3];int a = fis.read(bytes);System.out.println(a);System.out.println(new String(bytes));int b = fis.read(bytes);System.out.println(b);System.out.println(new String(bytes));int c = fis.read(bytes);System.out.println(c);System.out.println(new String(bytes));int d = fis.read(bytes);System.out.println(d);System.out.println(new String(bytes));}
}

由于每次读到内存中的byte数组中的数据不会刷新而会覆盖，当读到最后的数据不足字节数组的长度时则会出现数据重复，因而可以使用方法new String(byte[] bytes,int offset,int length);来获取每次读到的有效数据长度

new String(byte[] bytes,int offset)

package io;
import java.io.FileInputStream;
import java.io.IOException;
public class ByteStream {public static void main(String[] args) throws IOException {String filePath = "src/io/temp.txt";FileInputStream fis = new FileInputStream(filePath);byte[] bytes = new byte[3];int temp;while ((temp = fis.read(bytes)) != -1){System.out.println(new String(bytes,0,temp));}}
}

FileOutputStream

文件字节输出流 将内存中的数据写入计算机硬盘中

void write(byte[] bytes)

package io;
import java.io.FileOutputStream;
import java.io.IOException;
public class ByteStream {public static void main(String[] args) throws IOException {String filePath = "src/io/temp";       //文件不存在则自动创建FileOutputStream fos = new FileOutputStream(filePath,true);//true表示追加写，默认为false覆盖写String s = "Hello World";byte[] bytes = s.getBytes();fos.write(bytes);fos.close();}
}

void write(byte[] bytes,int offset,int length)

将字节数组的一部分写入

使用字节流完成文件的复制

package io;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class ByteStream {public static void main(String[] args) throws IOException {String filePath = "src/io/temp";FileInputStream fis = new FileInputStream(filePath);FileOutputStream fos = new FileOutputStream("src/io/temp.txt",true);byte[] bytes = new byte[1024];int temp;while((temp = fis.read(bytes)) != -1){fos.write(bytes,0,temp);}fos.close();fis.close();}
}

FileReader

文件字符输入流

package io;
import java.io.FileReader;
import java.io.IOException;
public class CharStream {public static void main(String[] args) throws IOException {String filePath = "src/io/temp";FileReader fr = new FileReader(filePath);char[] ch = new char[512];int temp;while((temp =fr.read(ch)) != -1){System.out.println(new String(ch,0,temp));}}
}

FileWriter

文件字符输出流

package io;
import java.io.FileWriter;
import java.io.IOException;
public class CharStream {public static void main(String[] args) throws IOException {String filePath = "src/io/temp";FileWriter fw = new FileWriter(filePath,true);String s = "hello";char[] ch = {'h','e','l','l','o'};fw.write(s);          //直接写入字符串fw.write(s,0,2);      //写入部分字符串fw.write(ch);         //写入字符数组fw.write(ch,0,3);     //写入部分字符数组fw.close();}
}

使用字符流完成文件的复制

package io;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class CharStream {public static void main(String[] args) throws IOException {FileReader fr = new FileReader("src/io/temp");FileWriter fw = new FileWriter("src/io/temp.txt",true);char[] ch = new char[512];int temp;while((temp = fr.read(ch)) != -1){fw.write(ch,0,temp);}fw.close();fr.close();}
}

BufferedInputStream

带有缓冲区的字节输入流

BufferedOutputStream

带有缓冲区的字节输出流

BufferedReader

带有缓冲区的字符输入流

package io;
import java.io.*;
public class CharStream {public static void main(String[] args) throws IOException {BufferedReader br= new  BufferedReader(new FileReader("src/io/temp"));String temp;while((temp = br.readLine()) != null){  //每次读取一行System.out.println(temp);}}
}

package io;
import java.io.*;
public class CharStream {public static void main(String[] args) throws IOException {BufferedReader br= new  BufferedReader(new FileReader("src/io/temp"));char[] ch = new char[512];int temp;while ((temp = br.read(ch)) != -1){   //每次读取一个kSystem.out.println(new String(ch,0,temp));}}
}

package io;
import java.io.*;
public class CharStream {public static void main(String[] args) throws IOException {BufferedReader br= new  BufferedReader(new FileReader("src/io/temp"));char[] ch = new char[512];int temp;while ((temp = br.read(ch,0,1)) != -1){     //每次只会读取一个字符长度的数据存到数组中System.out.println(new String(ch,0,temp));}}
}

BufferedWriter

带有缓冲区的字符输出流

package io;
import java.io.*;
public class CharStream {public static void main(String[] args) throws IOException {BufferedWriter bw= new BufferedWriter(new FileWriter("src/io/temp",true));bw.write("hello");bw.newLine();         bw.close();}
}

BufferedWriter和FileWriter使用方法差不多，前者可以换行

使用BuffferedReader和BufferedWriter

package io;
import java.io.*;
import java.util.*;
public class Io_ArrayListRandom {public static void main(String[] args)  throws IOException {BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream("src/io/temp"), "GBK"));ArrayList<String> arr = new ArrayList<>();String s;while ((s = br.readLine()) != null) {arr.add(s);}br.close();Random r = new Random();int index = r.nextInt(arr.size());//产生大小在集合长度范围内的下标System.out.println(arr.get(index));arr.remove(index);                //移出随机产生下标对应的数据        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("src/io/temp", true), "GBK"));for (String name : arr) {         //将剩下的数据写入原来文件中bw.write(name);bw.newLine();}bw.close();}
}

InputStreamReader

转换流（字节输入流 --> 字符输入流 ）

BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream("src/io/temp")));

OutputStreamWriter

转换流（字节输出流 --> 字符输出流 ）

BufferedWriter bw= new BufferedWriter(new OutputStreamWriter(new FileOutputStream("src/io/temp",true)));

PrintStream

标准的输出流，默认以字节的方式打印到控制台

PrintStream ps = System.out;
ps.println("");        ---> System.out.println("");

package io;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintStream;
import java.text.SimpleDateFormat;
import java.util.Date;
public class Io_PrintStream {public static void main(String[] args) {try{//System默认打印到控制台PrintStream ps = System.out;ps.println("java");//通过setOut方法改变打印输出方向System.setOut(new PrintStream(new FileOutputStream("src//io//log")));System.out.println(new SimpleDateFormat("yyyy-MM-dd HH-mm-ss").format(new Date()));System.out.println("打印日志");}catch (FileNotFoundException e){e.printStackTrace();}}
}

PrintWriter

以字符方式

package io;
import java.io.*;
public class Io_PrintStream {public static void main(String[] args) throws IOException {PrintWriter pw = new PrintWriter(new FileWriter("src/io/temp",true));String[] dest = new String[]{"hello","world"};for(String s : dest){pw.println(s);      //自动刷新和换行}pw.close();             //必须关闭}
}

boolean endWith()

寻找所有以.dll结尾的文件

package io;
import java.io.File;
public class File_ListFiles {public static void main(String[] args) {String filePath = "";File f = new File(filePath);File [] files = f.listFiles();for(File file:  files) {if(file.isFile()) {if(file.getName().endsWith(".dll")) {System.out.println(file.getName());}}}}
}

package io;
import java.io.File;
public class File_ListFiles {public static void main(String[] args) {String filePath = "";File folder = new File(filePath);File[] fileArray = folder.listFiles((dir, name) -> new File(dir, name).isFile() && name.endsWith(".dll"));assert fileArray != null;for (File file : fileArray) {System.out.println(file.getName());}}
}

递归遍历一个文件夹下所有的文件

package io;
import java.io.File;
public class FileList_Java {public static void fileList(File target) {if (target.isFile()) {return;}File [] files = target.listFiles();for(File file : files){System.out.println(file.getName());fileList(file);}}public static void main(String[] args) {String filePath = "";fileList( new File(filePath));}
}

复制文件并更改后缀名

package io;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class Io_ChangeName {public static void copy(File file,File newFile)throws IOException {BufferedInputStream  fis = new BufferedInputStream(new FileInputStream(file));BufferedOutputStream fos = new BufferedOutputStream(new FileOutputStream(newFile,true));byte []bs = new byte[1024];int len;while((len = fis.read(bs)) != -1) {fos.write(bs,0,len);}fos.close();fis.close();}public static void main(String[] args) throws IOException {String targetFile = "";String destFile = "";File target = new File(targetFile);File  dest = new File(destFile);if(!dest.exists()) ff.mkdir();File[] files = target.listFiles();assert files != null;for(File file : files) {String name = file.getName();System.out.println(name);name = name.replace(".java", ".txt");File newFile = new File(dest,name);copy(file,newFile);}}
}

Scanner

package io;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class Io_Scanner {public static void main(String[] args){try{File file = new File("src/io/temp");Scanner sc = new Scanner(file);while (sc.hasNext()) {System.out.println(sc.next());}sc.close();} catch (FileNotFoundException e) {e.printStackTrace();}}
}

LineNumberReader

package io;
import java.io.FileReader;
import java.io.IOException;
import java.io.LineNumberReader;
public class Io_LineNumberReader {public static void main(String[] args) throws IOException {LineNumberReader  lnr = new LineNumberReader(new FileReader("src/io/temp"));String s;lnr.setLineNumber(100);              //设置起当前行数while((s = lnr.readLine()) != null) {System.out.println(lnr.getLineNumber()+":"+s);}lnr.close();}
}

ByteArrayOutputStream

内存操作流：数据在内存中转一圈

package io;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
public class Io_ByteArray {public static void main(String[] args) throws IOException {ByteArrayOutputStream baos = new ByteArrayOutputStream();baos.write("hello".getBytes());byte[] bs = baos.toByteArray();ByteArrayInputStream  bais = new ByteArrayInputStream(bs);int len;while((len = bais.read()) != -1){System.out.print((char) len);}}
}

• 磁盘操作：File
• 字节操作：InputStream 和 OutputStream
• 字符操作：Reader 和 Writer
• 对象操作：Serializable
• 网络操作：Socket
• 新的输入/输出：NIO

复制图片，视频，音频等：只能用字节流,而不能使用字符流

复制纯文本可以使用字符流.

用字节流向文件中写入数据时，必须要转换为字节类型或用字节数组，比如字符串是直接写不进去的

而用字符流时用字符串和字符都行

字节流在使用后没有关闭写数据管道时仍然可以成功写入数据（带有缓冲区的除外）

字符流在使用后没有关闭写数据管道时，此时写入数据失败，系统就会认为还有数据一直在等待中，使用flush方法强行写入

通过键盘输入的两种方法

1:通过Scanner方法

 Scanner sc = new Scanner(System.in);//System.in是一个标准的输入流 默认接受键盘的输入

2:通过BufferedReader

BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
String s = input.readLine();
input.close();