About IO streams in Java: stream inheritance relationships, processing streams, and conversion streams

1. The inheritance relationship of streams, as well as byte streams and character streams.

2. Node streams FileOutputStream and FileInputStream and processing streams BufferedInputStream and BufferedOutputStream. And the corresponding FileOutputWriter, FileInputReader, BufferedInputReader, BufferedOutputWriter.

3. Convert streams InputStreamReader and OutputStreamWriter

1: Stream inheritance relationship

Byte stream

Character stream

Usage scope of character stream and byte stream: Byte stream is generally used to process images, videos, and PPT, Word type files . Character streams are generally used to process plain text files, such as TXT files, etc. Byte streams can be used to process plain text files, but character streams cannot be used to process non-text files such as images and videos.

2: Processing streams BufferedReader, BufferedWriter, BufferedInputStream

BufferedOutputsStream must include the upper layer of node streams. In other words, the processing stream is based on the node stream. The stream with Buffered is also called a buffered stream. The buffered stream processes the input and output of files the fastest. Therefore, buffered streams are generally used more frequently.

The following are two simple examples of file copying:

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public class MycopyTest { public static void main(String[] args) { File src = new File("D:/1.jpg" ); // D:/1.jpg must exist otherwise an error will be reported File dest = new File("D:/2.jpg" ); // If D:/2.jpg exists, overwrite it, if it does not exist, create a new one streamCopy(src, dest); } private static void readCopy(File src,File dest) { FileReader fr=null; FileWriter fw=null; BufferedReader br=null; BufferedWriter bw=null; try {       fr=new FileReader(src);       fw=new FileWriter(dest);       br=new BufferedReader(fr);       bw=new BufferedWriter(fw);       String str;      while((str=br.readLine())!=null)         {         bw.write(str);         bw.newLine();       }     }catch (IOException e) {       // TODO Auto-generated catch block       e.printStackTrace();     }     try {       bw.close();       br.close();     } catch (IOException e) {       // TODO Auto-generated catch block       e.printStackTrace();     }     }   private static void streamCopy(File src, File dest) {     FileInputStream fis = null;     FileOutputStream fos = null;     BufferedInputStream bis = null;     BufferedOutputStream bos = null;     try {       fis = new FileInputStream(src);       fos = new FileOutputStream(dest);       bis = new BufferedInputStream(fis);       bos = new BufferedOutputStream(fos);       int len;       byte[] b = new byte[1024];       while ((len = bis.read(b)) != -1) {         bos.write(b, 0, len);         // bos.write(b,0,len);是把读到数组的大小字节写入         // bos.write(b);最后一次如果数组未写满的话就会多读。       }     } catch (IOException e) {       // TODO Auto-generated catch block       e.printStackTrace();     }     try {       bos.close();       bis.close();     } catch (Exception e) {       // TODO Auto-generated catch block       e.printStackTrace();     }   } }

Three: Conversion stream InputStreamReader and OutputStreamWriter

The role of conversion stream, when the text file is stored in the form of byte stream on the hard disk, After reading through InputStreamReader, it is converted into a character stream for processing by the program. The character stream processed by the program is converted into a byte stream through OutputStreamWriter and saved.

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public class InputStreamWriterTest { public static void main(String[] args) { File src = new File("D:/Files/Shit.txt"); File dest = new File("D:/Files/Smith.txt" ); BufferedWriter bw = null; BufferedReader br = null; FileInputStream fis = null; FileOutputStream fos = null; try { fis = new FileInputStream(src); fos = new FileOutputStream(dest);      InputStreamReader ir = new InputStreamReader(fis, "GBK");      OutputStreamWriter ow = new OutputStreamWriter(fos, "GBK");       bw = new BufferedWriter(ow);        br = new BufferedReader(ir);        String str;        while ((str = br.readLine()) != null) {         bw.write(str);         bw.newLine();          bw.flush();        } } catch (IOException e) {        e.printStackTrace(); } try {         bw.close();        br.close(); } catch (IOException e) {        e.printStackTrace(); } } }

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