一个简单的java重定向程序，为什么要恢复System . out 对象，却不要恢复System . in对象

Question

import java . io .* ;

public class StandardIO
{
        public static void main (String [ ] args) throws IOException
        {
                
                PrintStream console = System . out ;
                // InputStream stdin = System .in ;         // 为什么不需要恢复该对象
                BufferedInputStream in = new BufferedInputStream ( 
                        new FileInputStream ("StandardIO.java")) ; 
                PrintStream out = new PrintStream (
                        new BufferedOutputStream (
                                new FileOutputStream ("test.out"))) ;
                System . setIn (in) ; 
                System . setOut (out) ;
                System . setErr (out) ;
                BufferedReader br = new BufferedReader ( 
                        new InputStreamReader (System . in )) ;
                String s ;
                while ( ( s = br . readLine ( ) ) != null )
                {
                        System . out . println ( s ) ;
                }
                out . close ( ) ;
                System . setOut (console) ;
        } 
}

Answer 1

You can also try not to restore System.out and see what happens.
Theoretically speaking, the program is over and it doesn’t matter whether it is restored or not.