Standard input stream and standard output stream for Java 21-11 IO streams

Standard input/output stream
Two member variables in the system class:
public static final InputStream in "standard" input stream.
public static final PrintStream out "standard" output stream.

Pnputstream is = system.in;
PrintStream PS = System.out;

System.out; Standard output stream:

You can see it from the top, actually.

        System.out.println ("HelloWorld");

actually equals

        PrintStream PS = System.out;        Ps.println ("HelloWorld");

Attention:　　

1 printstream PS = System.out; 2 //The following two methods, in fact, is a method does not exist, note: () nothing inside.  3ps.print (); 4 System.out.print ();

Let's play something interesting:

How do I make a byte stream into a character stream to manipulate it?

We can play by converting streams, byte stream → convert stream → character stream

1      Public Static voidMain (string[] args)throwsIOException {2                 //get standard input stream3                 // //PrintStream PS = System.out;4                 // //outputstream OS = PS;5                 //outputstream os = system.out;// polymorphic6                 // //we use a character stream to wrap the character stream, the surface is a stream of characters, in fact, the bottom is the byte stream (standard output stream)7                 //OutputStreamWriter OSW = new OutputStreamWriter (OS);8                 //bufferedwriter bw = new BufferedWriter (OSW);9BufferedWriter BW =NewBufferedWriter (NewOutputStreamWriter (Ten System.out)); One  ABw.write ("Hello"); - bw.newline (); -Bw.write ("World"); the bw.newline (); - Bw.flush (); -                  - bw.close (); +}

。。。 If you're going to die, just understand.

system.in; Standard input stream:

The input stream and the output stream are about the same. Here's an interesting thing:

To JDK1.7, there are 3 ways to achieve keyboard entry:

1, the main method of the args receive parameters:　　　　

Java HelloWorld Hello World Java

　　2, Scanner (JDK1.5 later)

1 New Scanner (system.in); 2 String s = sc.nextline (); 3 int x = sc.nextint (); 4 ...

Well, before JDK1.5, this is the way:

3, through the character buffer stream packaging standard input stream implementation:

1      Public Static voidMain (string[] args)throwsIOException {2         // //get standard input stream3         //InputStream is = system.in;4         //However, this can only fetch one byte at a time. And what we want is to get one row of data at a time5         //To achieve this, first you need to know which way to read one row of data at a time?6         //ReadLine ()7         //and this method is in the BufferedReader class, so we should create the BufferedReader object, but the underlying is still using the standard input stream8         //bufferedreader br = new BufferedReader (is);9         //But there's still an error here. The reason is that the character buffer stream can only be manipulated for character streams, and InputStream is a byte stream, so you cannot useTen         //If you want to use it, you can only convert the byte stream to a character stream and then manipulate it through the character buffer stream. One          A         //InputStreamReader ISR = new InputStreamReader (is); -         //BufferedReader br= New BufferedReader (ISR); These two sentences can be written in the following sentence -BufferedReader br =NewBufferedReader (NewInputStreamReader (system.in)); the  -System.out.println ("Please enter a string:"); -String line =br.readline (); -System.out.println ("The string you entered is:" +Line ); +  -System.out.println ("Please enter an integer:"); +         //int i = Integer.parseint (Br.readline ()); Aline =br.readline (); at         inti =Integer.parseint (line); -System.out.println ("The Integer you entered is:" +i); -}

Conclusion:... Let's just use scanner.

　　

Standard input stream and standard output stream for Java 21-11 IO streams