I am trying to derive a validation code in which the

Question

I am trying to derive a validation code in which the program would produce a computational answer when executed.For this question the numbers are assumed to be 4 digit numbers. The program may assume it has received a valid 4 digit number. The validation is based on adding the first digit, two times the second digit, and the third digit and considering the last digit of this computation.

Output:

Please enter a 4 digit number: 1234
The last digit is 4
The last digit of the computed result 8 is 8

my code:

import java.util.Scanner;

public class validate {

 public static void main(String[] args) {

  int first_dig, second_dig, third_dig, last_dig, comp_number,four_digits;

  Scanner by;

  by=new Scanner(System.in);

  System.out.println("Please enter a four digit number");

  four_digits=by.nextInt(first_dig + second_dig +third_dig + last_dig);

 }

}