Java IO (v): selection rule of Byte stream and character stream

Byte stream, character stream involves more analogy, more easily confused. Therefore, it is necessary to make a generalization about when to use a byte stream, when to use a character stream, and when to use a stream of the buffer class. To generalize them, you don't need too many languages, just grab their focus and features.

Here are a few questions to consider when deciding when to use which class.

1. Whether there is a data source, whether the flow of data has a target.
   • Data source: represents input, or read. The two parent classes available for use are inputstream and reader.
   • Target: Represents the output, or is called write. The two parent classes available for use are OutputStream and writer.
2. Should I use a byte stream or a character stream? If the source or destination contains non-ASCII characters, a character stream is used.
3. What device type the source and destination are.
   • Source: Disk File, Memory (Byte/character array), keyboard system.in, network socket
   • Target: Disk file, Memory (Byte/character array), screen System.out, network socket
4. Do I need to use Bufferedreader/bufferedwriter? This will need to consider whether additional special features are required, including operation Lines, character set conversions, and the use of buffers to improve efficiency . The process of converting a byte stream into a character stream is involved in character set conversion, and it may be necessary to use InputStreamReader and OutputStreamWriter as a bridge for conversion.

Finally, it is necessary to know that for an input stream using BufferedReader, it is sometimes possible to consider using a character array for better results and performance.

Here is an example of a requirement to apply the above rules: read the file data that contains GBK Simplified Chinese and copy it to another file with Utf-8 encoding.

1. The source has a target, and all are files. 2. Both read and write contain Chinese characters, so a character stream is used. 3. Transcoding is required during the write process, so you need to use OutputStreamWriter. 4. You can use the buffer function to improve efficiency.

Importjava.io.*; Public  class CP {Public   static void main(string[] args) throws IOException{File src =NewFile ("D:/myjava/a.txt"); File dest =NewFile ("D:/myjava/a_bak.txt");    CP (Src,dest); }Public   static void cp(File src,file dest) throws IOException{BufferedReader BUFR =NewBufferedReader (NewFileReader (SRC)); BufferedWriter BUFW =NewBufferedWriter (NewOutputStreamWriter (NewFileOutputStream (dest),"Utf-8"));//Read by lineString line =NULL; while((Line=bufr.readline ())! =NULL) {Bufw.write (line);            Bufw.newline ();        Bufw.flush ();    } bufw.close (); }}

After the above code executes, the end of the target file will be more than a blank line in the source file, the above method is not a good solution to this problem. However, if you use a character array instead of BufferedReader, there is no such problem, as follows.

Importjava.io.*; Public  class CP {Public   static void main(string[] args) throws IOException {File src =NewFile ("D:/myjava/a.txt"); File dest =NewFile ("D:/myjava/a_bak.txt");    CP (Src,dest); }Public   static void cp(File src,file dest) throws IOException{FileReader FR =NewFileReader (SRC); BufferedWriter BUFW =NewBufferedWriter (NewOutputStreamWriter (NewFileOutputStream (dest),"Utf-8"));Char[] buf =New Char[1024x768];intLen =0; while((Len=fr.read (BUF))!=-1) {Bufw.write (buf,0, Len);    Bufw.flush ();    } bufw.close (); }}

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Java IO (v): selection rule of Byte stream and character stream