I wrote a code to add four numbers together from a string but the answer is 192 bigger than its supposed to be

Question

This is my code:

import java.util.Scanner;
public class Main {
public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);

    int num = sc.nextInt();

    for(int i = 0; i <= num; i++){
        String calculation = sc.next();
        String b = sc.next();
        int sum = 0;

        if(calculation.equals("ADD")){
            int num2 = Integer.parseInt(b);
            int num3 = String.valueOf(Math.abs((long)num2)).charAt(0);
            int num4 = String.valueOf(Math.abs((long)num2)).charAt(1);
            int num5 = String.valueOf(Math.abs((long)num2)).charAt(2);
            int num6 = String.valueOf(Math.abs((long)num2)).charAt(3);          
            sum = num3 + num4 + num5 + num6;
        }
        System.out.println(sum - 192);
    }
}}

If the input is: 1 ADD 1234 Then the answer would be 202 instead of 10. I'm not sure where my code is wrong.

192 is 48 x 4 and 48 is ascii value of 0. So, it seems like the charAt(x) returns ascii value of integer at index x — 2rd_7, Jun 11 '16 at 16:08
I think You'll understand why the final result is not the one you wish when you understand why num 3 = 49 — kevin ternet, Jun 11 '16 at 16:31

score 1 · Accepted Answer · answered Jun 11 '16 at 16:26

You are adding the ascii code of 1,2,3 and 4 all together, which is 202. Your code is all wrong:

It is useless to cast an int into a long and into an int again without doing operations on it.
If the number may be negative, then take its absolute value only once and not for each digit.
num2 is an int: 1234
String.valueOf((long)num2) is a String: "1234"
String.valueOf((long)num2).charAt(0) is a char: '1'

So, sum is litterally equals to '1' + '2' + '3' + '4'.

Just remove those unnecessary (and ugly) casts:

int num3 = b.charAt(0) - '0';
int num4 = b.charAt(1) - '0';
int num5 = b.charAt(2) - '0';
int num6 = b.charAt(3) - '0';          
sum = num3 + num4 + num5 + num6;

Or you can do it in one line:

sum = b.charAt(0) + b.charAt(1) + b.charAt(2) + b.charAt(3) - 4*'0';

There is probably a way to do it using lambdas as well. If you want to be a bit more secure, use a loop (a number does not always have 4 digits):

int sum = 0;
for (char c : b.toCharArray()) {
    if (c >= '0' && c <= '9') sum += c - '0';
}

There are better ways to convert characters to digits - http://stackoverflow.com/questions/19388037/converting-characters-to-integers-in-java (which I believe can serve as essentially duplicate of this question) — Alexei Levenkov, Jun 11 '16 at 20:56

I wrote a code to add four numbers together from a string but the answer is 192 bigger than its supposed to be

1 Answers1