I do not understand what the % accomplishes in this context.

Question about the task

Sum of the digits of a three-digit number

Under discussion

The code I have is not even technically my own. I looked around at all the questions, I copied this down, but I still don't understand any of it. What does number%10 do? Why do we do number = number / 10 + number / 10 + number / 10? I don't understand the concept, did I miss when this was taught to us? Pls Help.

Write the code for sumDigitsInNumber(int number). The method takes a three-digit whole number. You need to calculate the sum of the digits of this number, and then return the result.

Consider this example:
The sumDigitsInNumber method is called with the argument 546.

Example output:
15

Requirements:

The program must not read data from the keyboard.
The sumDigitsInNumber(int) method must be public and static.
The sumDigitsInNumber method must return an int.
The sumDigitsInNumber method should not display anything.
The sumDigitsInNumber method must return the sum of all digits in the parameter number.

package com.codegym.task.task01.task0132; /* Sum of the digits of a three-digit number */ public class Solution { public static void main(String[] args) { System.out.println(sumDigitsInNumber(546)); } public static int sumDigitsInNumber(int number) { int sum; int n; while (number>=0){ n = number%10; sum = sum + n; number = number / 10 + number / 10 + number / 10; } return sum; //write your code here } }

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Daniel

Level 9 , Vienna, Austria

9 June 2020, 10:51

number = number / 10 + number / 10 + number / 10; <--This is actually wrong. The person who wrote the code thought that by dividing the number and summing the result it he/she will end up with the sum. The loop never ends in that case. number = number / 10; This was enough to just get rid of the last digit in the number. The reminder is used to split the numbers then sum them. Modulus(%) 10 is used to take out the reminder. division to 10 is used to take out the last digit and continue.

Step 1.
n  =  number % 10;
n is the reminder of number modulus 10

Step 2.
sum = sum + n
take the reminder and add it to sum

Step 3.
number = number / 10;
the number is divided by 10 and put it back into number variable so that the last digit goes away and continue with the modulus operation and take out the next reminder out, otherwise you will end up with no reminder and a continous loop wich ads the last reminder to your number. The division of 2 integers in java will end up in a result with no reminder. Ex: 13/2 = 6, 48/7 = 6. 546/10 = 54

I hope this helps.

Gellert Varga

Level 23 , Szekesfehervar, Hungary

8 June 2020, 19:47

You didn't miss. They won’t always explain everything super-thoroughly in this course. It is the expectation sometimes: to look for something, to search with google, and to think. % = "division with remainder" ((my english is... ... maybe i don't say it correctly.)) The remainder matters. Examples: 1% 3 = 1 2% 3 = 2 3% 3 = 0 4% 3 = 1 etc. Do not copy codes. Think. And ask. And try out the programs a lot of times, and always observe the outputs. You can learn from this. But if you get some hints, you can search with google and find tutorial sites about it for pupose of understanding. The understanding is the most important.