Java I/O - 如何取一个字符串并将其放在System.in中

import java.io.ByteArrayInputStream;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        String str = "w3cschool.cn";
        ByteArrayInputStream bais = new ByteArrayInputStream(str.getBytes());
        System.setIn(bais);

        Scanner scanner = new Scanner(System.in);
        String input = scanner.next();
        System.out.println(input);
    }
}