Java - System.setIn() Examples

package com.logicbig.example.system;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

public class SetInExample {

    public static void main(String... args) throws IOException {

        File file = new File("D:\\test\\one.txt");

        System.out.println("file exits: "+file.exists());

        FileInputStream stream = new FileInputStream(file);
        System.setIn(stream);

        System.out.println("-- reading from System.in --");

        byte[] data = new byte[1000];
        System.in.read(data);
        System.out.println(new String(data));
    }
}

Output

file exits: true
-- reading from System.in --
file one content