Java. How to add primitive values in a loop - (for)

Question

I'm trying to take a random number and split it, then add its digits, so the number "3457" will be........ 3 + 4 + 5 + 7. But I've come across the problem of having to add the values in the loop but i find it difficult since most of my types within my loop are primitive types thus i cant really use the "nextInt()" method... So down to my question... how do you add values within a loop. Here's my code so far...

import java.util.Scanner;
public class HellloWorld {

    public static void main(String[] args) {
       Scanner input = new Scanner(System.in);
           try {
           System.out.println("Please Enter your number: " + "\n");
           int int1 = Integer.parseInt(input.next());
           int life = String.valueOf(int1).length();
           for (int i = life; i >= 1; i--) {
           int int2 = int1 / (int)(Math.pow(10, i-1));
           int int3 = int2 % (int)(Math.pow(10,1));

               if (i == 1) {
            System.out.print(int3 + " = ");
        } else {
            System.out.print(int3 + " + ");
        }
    }

    } finally {
        input.close();
    }
}
}

Answer 1

You can do this using Stream like this:

public static void main(String... args) {
  Scanner sc = new Scanner(System.in);
  String strNum = sc.next();
  int sum = Arrays.stream(strNum.split(""))
              .mapToInt(str -> Integer.parseInt(str))
              .sum();
  System.out.println(sum);
}

Answer 2

1. For the sum case - You can use another variable, lets say sum somewhat as -

    int sum = 0; for(...) { .... sum = sum + yourDigit; if{...} else {...} } //end of for loop System.out.println(sum); 

2. Your logic seems not to be doing the sum - try using (1) to see if you get what is desired.

3. Think of

    int sum = 0; int input = int1; while (input != 0) { int lastdigit = input % 10; //(right to left) one's to tens to hundreds place value sum += lastdigit; // sum = sum + lastDigit input /= 10; // your if..else can be based on this value } 

Answer 3

My weird but epic way of doing it:

public static void main(String[] args) {
    int a = 1234;   //say you get that number somehow... lets say thru Scanner  
    String b = String.valueOf(a);   //convert to a string   
    int result = 0;     
    for (int i = 0; i < b.length(); i++) {
        result = result + Integer.parseInt(Character.toString(b.charAt(i))); // here a conversation is happening of epic scale
    }
            System.out.println("result is: "+ result);
}