Creating a method that can sum digits of an integer

Question

Hello,

I have been trying to solve this common problem in Java courses:

Sum the digits in an integer Write a method that computes the sum of the digits
in an integer. Use the following method header:
public static int sumDigits(long n)
For example, sumDigits(234) returns 9 (2 + 3 + 4). (Hint: Use the % opera-
tor to extract digits, and the / operator to remove the extracted digit. For instance,
to extract 4 from 234, use 234 % 10 ( = 4). To remove 4 from 234, use 234 / 10
(= 23). Use a loop to repeatedly extract and remove the digit until all the digits
are extracted. Write a test program that prompts the user to enter an integer and
displays the sum of all its digits.

This is the code that I have:

public class sumDigitMetho{
public static void main(String[] args) {
System.out.println(sumDigitMetho(234));

}

public static int sumDigitMetho(long n){

long result = 0;
for(long x = n; x <=n ;x++){
x=x%10/10;
result += x;
return x;

}

}
}

Every time I compile I get the response: "incompatible types: possible lossy conversion from long to int.
return x;

What am I doing wrong? I know I do not have the user input yet

Thanks,

Sei

Answer 1

Your sumDigitMethof is as integer declared but return a long.
It must be long too.

Answer 2

Also you need to return outside the loop

Answer 3

Sei

So far you have many problem.

1 - take parameter as a int because int is enough to handle such a long value 234

2 - x = n; x <= n; causes infinite loop because 234 <= 234 will be always true

3 - change result as int

4 - x = x % 10 / 10 is wrong because 234 % 10 / 10 = 4 / 10 = 0

So x would be 0 after 1st iteration and result would be 0

5 - return should be outside the loop

6 - for loop works for fix length of iteration as we don't know so this problem can be easily solve using while loop

public static int sumDigitMetho(int n) {

int result = 0;

while (n > 0) {
//x=x%10/10;
result += n % 10;
// return x;
n = n / 10;

}

return result;

}

Answer 4

Sei ,
This code shows one solutions way:

https://code.sololearn.com/cuA27LS8xH8e/?ref=app

Answer 5

An "easy" solution is to change all of your long values to ints. Are the numbers going to be so large that you'll need a long?

Answer 6

Sei , just check on how big the numbers can reasonably get. If you need long, go for long. I really doubt a sum of digits would overflow an int.
But the function must return the same type it is declared. You declared an int function and tried to return a long. Make it equal.

Answer 7

Side note: in the for loop, you're changing the loop variable (x) both in the loop declaration and inside it. This smells trouble.

Answer 8

You guys are awesome! Thank you all for your help. I'm not in a formal class at the moment, just myself using a textbook.

But I do have another question: Some of the posts have suggested that I use int instead of long why is this? I know in the example I substituted 234 for the formal parameters but it could have been a much larger number.

Thanks Again

Answer 9

JaScript,

Thanks!

Answer 10

You are welcome Sei!