IO

流！

分为两类：字符流，和字节流

一、字符流：Wirter,Reader==>FileWriter，FileReader==>BufferedReader，BufferedWriter

1，字符的写入

public static void main(String[] args) {String path = "D:\\IO\\io.txt";FileWriter fileWriter=null;try {fileWriter = new FileWriter(new File(path)); //fileWriter = new FileWriter("D:\\IO\\io.txt");  可以直接填写路径，也可以new出新的filefileWriter.write("zheshigeceshi这是个测试IO,呵呵哒");/*fileWriter.flush();  //如果不加这个立即写入的话，只能关闭流之后才能写入。*/} catch (IOException e) {e.printStackTrace();}finally {if(fileWriter !=null){try {fileWriter.close();  //关闭流} catch (IOException e) {e.printStackTrace();}}}}

2，字符的读取

public static void main(String[] args) {String path = "D:\\IO\\io.txt";FileReader fileReader = null;try {fileReader = new FileReader(new File(path));int temp = 0;char[] chars = new char[1024];   //是char[]  字符串    while ((temp =fileReader.read(chars)) != -1) {String string = new String(chars, 0, temp);System.out.println(string);}} catch (IOException e) {e.printStackTrace();}finally {if(fileReader !=null){try {fileReader.close();} catch (IOException e) {e.printStackTrace();}}}}

3，文件的复制（使用fileReader，fileWriter）

public static void main(String[] args) {String path = "D:\\IO\\io.txt";String copyPath = "D:\\IO\\ioCopy.txt";FileReader fileReader=null;FileWriter fileWriter=null;try {fileReader = new FileReader(new File(path));  //new 对象fileWriter = new FileWriter(new File(copyPath));int temp = 0;char[] bs = new char[1024];String string = null;while ((temp = fileReader.read(bs)) != -1) {  //读数据string = new String(bs, 0, temp);fileWriter.write(string);   //写数据，如果不关闭流，则不写入}} catch (IOException e) {e.printStackTrace();}finally {   //关闭流if(fileReader !=null) {try {fileReader.close();} catch (IOException e) {e.printStackTrace();}}if(fileWriter !=null){try {fileWriter.close();} catch (IOException e) {e.printStackTrace();}}}}

4，文件的复制（使用BufferedReader，BufferedWrite  利用缓冲区，快速的读写能力）

public static void main(String[] args) {BufferedReader bReader =null;BufferedWriter bWriter = null;try {bReader = new BufferedReader(new FileReader(new File("D:\\IO\\io.txt")));bWriter = new BufferedWriter(new FileWriter(new File("D:\\IO\\ioCopy.txt")));String line= null;while ((line = bReader.readLine()) !=null) {bWriter.write(line);System.out.println(line);  //输出每行的内容bWriter.newLine();  //接着读取下一行}} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally {if (bReader != null) {  //关闭缓冲区，就能关闭流对象了try {bReader.close();} catch (IOException e) {e.printStackTrace();}}if (bWriter !=null) {try {bWriter.close();} catch (IOException e) {e.printStackTrace();}}}}

二、字节流：InputStream，OutputStream==>FileInputStream,FileOutputStream==>BufferedInputStream,BufferedOutputStream

1，字节流的读取

public static void main(String[] args) {String pathname ="D:\\IO\\io.txt";FileInputStream fileInputStream =null;try {fileInputStream= new FileInputStream(new File(pathname));int temp = 0;byte[] b = new byte[1024];  // 是byte[]  字节while((temp = fileInputStream.read(b))!=-1){System.out.println(new String(b, 0, temp));}} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally {if(fileInputStream !=null){try {fileInputStream.close();} catch (IOException e) {e.printStackTrace();}}}}

2，字节流实现文件复制  （FileInputStream,FileOutputStream）

public static void main(String[] args) {String pathname ="D:\\IO\\io.txt";String pathCopyName ="D:\\IO\\ioCopy.txt";FileInputStream fileInputStream =null;FileOutputStream fileOutputStream =null;try {fileInputStream= new FileInputStream(new File(pathname));fileOutputStream = new FileOutputStream(new File(pathCopyName));int temp =0;byte[] b = new byte[1024];while((temp = fileInputStream.read(b))!=-1){System.out.println(new String(b, 0, temp));fileOutputStream.write(b, 0, temp);}} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally {if(fileInputStream !=null){try {fileInputStream.close();} catch (IOException e) {e.printStackTrace();}}}}

2，字节流实现文件复制  （BufferedInputStream,BufferedOutputStream）

<strong></strong>public static void main(String[] args) {String pathname ="D:\\IO\\io.txt";String pathCopyName ="D:\\IO\\ioCopy.txt";BufferedInputStream bufferedInputStream =null;BufferedOutputStream bufferedOutputStream=null;try {bufferedInputStream = new BufferedInputStream(new FileInputStream(new File(pathname)));bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(new File(pathCopyName)));int temp =0;byte[] b = new byte[1024];while((temp=bufferedInputStream.read(b))!=-1){System.out.println(new String(b, 0, temp));bufferedOutputStream.write(b, 0, temp);}System.out.println("复制完成！");} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally {if (bufferedInputStream != null) {try {bufferedInputStream.close();} catch (IOException e) {e.printStackTrace();}}if (bufferedOutputStream !=null) {try {bufferedOutputStream.close();} catch (IOException e) {e.printStackTrace();}}}}

三、问题来了

1，什么时候用字符流，什么时候用字节流？

   所谓字符流，肯定是用于操作类似文本文件，或者带有字符文件的比较多。

   所谓字节流，是操作那些无法直接获取文本信息的二进制文件，比如图片，mp3，视频文件等 说白了在硬盘上都是以字节存储的，只不过字符流在操作文本上面更方便一点而已

2，为什么使用缓冲区？

      硬盘本身是有缓冲区的，试想一下，如果一有数据，不论大小就开始读写，势必会给硬盘造成很大负担，它会感觉很不爽，人不也一样，一顿饭不让你一次吃完，每分钟喂一勺，你怎么想？因此，采用缓冲区能够在读写大文件的时候有效提高效率