자바8 왕초보 String scanner 사용에 대해 질문이 있습니다.

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
 
public class Solution {
 
    public static void main(String[] args) {
        int i = 4;
        double d = 4.0;
        String s = "HackerRank ";
 
        Scanner scan = new Scanner(System.in);
         /* Declare second integer, double, and String variables. */
        int i2;
        double d2;
        String s2;
        /* Read and save an integer, double, and String to your variables.*/
        i2 = scan.nextInt();
        d2 = scan.nextDouble();
        scan.nextLine();
        s2 = scan.nextLine();
        // Note: If you have trouble reading the entire String, please go back and review the Tutorial closely.
 
        /* Print the sum of both integer variables on a new line. */
        System.out.printf("%d\n", (i + i2));
        /* Print the sum of the double variables on a new line. */
		System.out.printf("%.1f\n", (d + d2));
        /* Concatenate and print the String variables on a new line; 
        	the 's' variable above should be printed first. */
         System.out.println(s + s2);
 
        scan.close();
    }
}