Envío 7090

Código

import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        StringBuilder num1 = new StringBuilder(scanner.nextLine()).reverse();
        StringBuilder num2 = new StringBuilder(scanner.nextLine()).reverse();
        int digit = 0;

        StringBuilder largerNum;
        StringBuilder shorterNum;
        if(num1.length() > num2.length()){
            largerNum = num1;
            shorterNum = num2;
        }else {
            largerNum = num2;
            shorterNum = num1;
        }

        StringBuilder result = new StringBuilder(largerNum);

        for (int i = 0; i < largerNum.length(); i++) {
            int sum;
            if(i < shorterNum.length()){
                sum = Character.getNumericValue(largerNum.charAt(i)) +
                        Character.getNumericValue(shorterNum.charAt(i)) + digit;
            }else{
                sum = Character.getNumericValue(largerNum.charAt(i)) + digit;
            }

            if(sum < 10){
                digit = 0;
                result.setCharAt(i, (char)(sum + '0'));
            }else{
                digit = 1;
                result.setCharAt(i, (char)((sum % 10) + '0'));
            }

            if((i == largerNum.length() - 1) && digit == 1){
                result.append('1');
            }
        }

        System.out.print(result.reverse());

        scanner.close();
    }
}