java学习笔记7对于将从控制台进行输入改为文件

import java.io.File;import java.io.OutputStream;import java.io.InputStream;import java.io.FileInputStream;import java.util.Scanner;public class Main{    public static void main(String [] agrs)    throws Exception    {        System.setIn(new FileInputStream(new File("D:"+File.separator+"imput.txt")));        Scanner cin=new Scanner(System.in);        int B=cin.nextInt();        System.out.println(B);    }}

此目的是将System.in所对应IO输入流进行重设