Java starts from scratch 38 (Java io-redirect IO)

一、三个 Static variables

Java.lang.System provides three static variables

• System.in (default keyboard)
• System.out (Default monitor)
• System.err

Second, rewrite to the method

The system provides three redirection methods

Method	Description
static void Seterr (PrintStream errr)	REDIRECT standard error output stream
static void SetIn (InputStream in)	REDIRECT Standard input stream
static void SetOut (PrintStream out)	REDIRECT Arrivals output stream

Iii. Example 3.1, redirect input stream

 PackageCom.pb.io.reio;ImportJava.io.BufferedReader;ImportJava.io.FileInputStream;Importjava.io.FileNotFoundException;Importjava.io.IOException;ImportJava.io.InputStreamReader;Importjava.io.UnsupportedEncodingException;/** REDIRECT Input * 1. There is an already initialized InputStream input stream * 2. Call the System.setin () method to redirect the standard input stream to the destination input stream * 3. Read the contents of the system.in*/ Public classReIn { Public Static voidMain (string[] args)throwsunsupportedencodingexception {Try {            //1. Declaring an input streamFileInputStream fis=NewFileInputStream ("D:/test/s1.txt"); //2. redirectionsystem.setin (FIS); //3. Read the contents of the system.in standard input streamBufferedReader br=NewBufferedReader (NewInputStreamReader (system.in, "gb2312"));//Set character encoding//4. Output the contents of the system.inString line=NULL;  while((Line=br.readline ())! =NULL) {System.out.println (line); }            //5. Close the streamBr.close ();        Fis.close (); } Catch(FileNotFoundException e) {e.printstacktrace (); } Catch(IOException e) {e.printstacktrace (); }    }}

3.2. REDIRECT Output stream

 PackageCom.pb.io.reio;Importjava.io.FileNotFoundException;ImportJava.io.FileOutputStream;ImportJava.io.PrintStream;/** redirect the output stream * 1. Initialize the PrintStream object * 2. Call the System.setout () method to redirect the subscript output stream to the PrintStream object * 3. Operation System.out Flow,*/ Public classReout { Public Static voidMain (string[] args) {Try {            //1. Declaring an output stream PrintStream objectPrintStream ps=NewPrintStream (NewFileOutputStream ("D:/test/ps.txt",true));//Append Content//2. Redirect the output streamSystem.setout (PS); //3. Using the PrintStream object to write information to the streamSYSTEM.OUT.PRINTLN ("The test redirect succeeded No!") "); System.out.println (Newreout ());        Ps.close (); } Catch(FileNotFoundException e) {e.printstacktrace (); }            }}

Java starts from scratch 38 (Java io-redirect IO)