java_IO流小结

字符流和字节流的主要区别：

1.字节流读取的时候，读到一个字节就返回一个字节；  字符流使用了字节流读到一个或多个字节（中文对应的字节数是两个，在UTF-8码表中是3个字节）时。先去查指定的编码表，将查到的字符返回。

2.字节流可以处理所有类型数据，如：图片，MP3，AVI视频文件，而字符流只能处理字符数据。只要是处理纯文本数据，就要优先考虑使用字符流，除此之外都用字节流。

   字节流：

   1、通过字节流写数据

code：

 package com.test;

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

 public class WriteByteStream {

     public static void main(String[] args) {
         try {

             FileOutputStream fos = new FileOutputStream("textw.txt");
             String outString = "write 123456写出数据";
             byte output[] = outString.getBytes("UTF-8");
             fos.write(output);
             fos.close();

         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (UnsupportedEncodingException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

 }

2、通过字节流读数据：

code：

 package com.test;

 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.UnsupportedEncodingException;

 public class ReadByteStream {

     public static void main(String[] args) {
         try {
             FileInputStream fis = new FileInputStream("text.txt");
             byte input[] = new  byte[];
             fis.read(input);

             String inputString = new String(input, "UTF-8");
             System.out.println(inputString);
             fis.close();

         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (UnsupportedEncodingException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }

     }

 }

3、使用字节流读写数据

code：

 package com.test;

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

 public class CopyByByteStream {

     public static void main(String[] args) {
         try {

             FileInputStream fis = new FileInputStream("movie.mp4");
             FileOutputStream fos = new FileOutputStream("movie_new.mp4");

             byte input[] = new byte[];
             long before = System.currentTimeMillis();
             int count = ;
             while (fis.read(input) != -) {
                 fos.write(input);
                 count++;
             }
             fos.flush();
             fis.close();
             fos.close();
             System.out.println(System.currentTimeMillis()-before+"ms");
             System.out.println("done");

         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

 }

4、使用带缓冲的字节流读写数据（字节流模板）

code：

 package com.test;
 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;

 public class ReadByBufferedByteStream {

     public static void main(String[] args) {
         try {

             FileInputStream fis = new FileInputStream("movie.mp4");
             BufferedInputStream bis = new BufferedInputStream(fis,);
             FileOutputStream fos = new FileOutputStream("moive_new.mp4");
             BufferedOutputStream bos = new BufferedOutputStream(fos,);
             //大型文件对应的数组可以大一些，小文件对应的数组小一些
             byte input[] = new byte[];
             int count = ;
             long before = System.currentTimeMillis();
             while (bis.read(input) != -) {
                 bos.write(input);
                 count++;
             }
             bos.flush();
             bis.close();
             fis.close();
             bos.close();
             fos.close();
             System.out.println(System.currentTimeMillis()-before+"ms");
             System.out.println("读取了："+count+"次");

         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

 }

  字符流：

  1、使用字符流读写数据

  code：

 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.OutputStreamWriter;
 import java.io.UnsupportedEncodingException;

 public class RWByCharStream {

     public static void main(String[] args) {
         try {

             //File file = new File("java.txt");
             FileInputStream fis = new FileInputStream("java.txt");
             FileOutputStream fos = new FileOutputStream("java_new.txt");
             InputStreamReader isr = new InputStreamReader(fis, "UTF-8");
             OutputStreamWriter osw = new OutputStreamWriter(fos, "UTF-8");
             char input[] = new char[];
             int l = ;
             while ((l = isr.read(input)) != -) {
                 //String inputString = new String(input,0,l);
                 osw.write(input,,l);
             }
             isr.close();
             fis.close();
             osw.close();
             fos.close();
             System.out.println("done");

         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (UnsupportedEncodingException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }

     }

 }

2、使用带有缓冲的字符流读写数据（字符流模板）

code：

 import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.OutputStreamWriter;
 import java.io.PrintWriter;
 import java.io.UnsupportedEncodingException;

 public class RWByBufferedCharStream {

     public static void main(String[] args) {
         try {

             //File file = new File("java.txt");
             FileInputStream fis = new FileInputStream("java.txt");
             FileOutputStream fos = new FileOutputStream("java_new_buff.txt");
             InputStreamReader isr = new InputStreamReader(fis, "UTF-8");
             OutputStreamWriter osw = new OutputStreamWriter(fos, "UTF-8");

             BufferedReader br = new BufferedReader(isr);
             //BufferedWriter bw = new BufferedWriter(osw);
             PrintWriter pw = new PrintWriter(osw,true);

             String input;
             while ((input = br.readLine()) != null) {
                 //bw.write(input);
                 pw.println(input);
             }
             br.close();
             //bw.flush();bw.close();
             pw.close();
             isr.close();
             fis.close();
             osw.close();
             fos.close();
             System.out.println("done");

         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (UnsupportedEncodingException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

 }