To do this, you will use the % (mod) operator.

int number; // = some int

while (number > 0) {
    print( number % 10);
    number = number / 10;
}

The mod operator will give you the remainder of doing int division on a number.

So,

10012 % 10 = 2

Because:

10012 / 10 = 1001, remainder 2

Note: As Paul noted, this will give you the numbers in reverse order. You will need to push them onto a stack and pop them off in reverse order.

Code to print the numbers in the correct order:

int number; // = and int
LinkedList<Integer> stack = new LinkedList<Integer>();
while (number > 0) {
    stack.push( number % 10 );
    number = number / 10;
}

while (!stack.isEmpty()) {
    print(stack.pop());
}

Your code prints 0 every time since it divides the number to 10 until it becomes 0 inside the while loop. Remember that any positive number below 10 divided by 10 gives the result 0 in Java.

You calculated the sum of digits correctly but did not check if it divides the number correctly. In order to achieve that, you need to store a copy of number at the start and check if it is divisible by sumOfDigits.

You can achieve the solution with the following code, it is very similar but structured a little better.

class Main
{
 
    // Function to check if the
    // given number is divisible
    // by sum of its digits
    static String divisableNumber(long n)
    {
        long temp = n; // store a copy of number
     
        // Find sum of digits
        int sum = 0;
        while (n != 0)
        {
            int k = (int) n % 10; // get remainder of division of 10
            sum += k; // add digit sum
            n /= 10; // divide number by 10
        }
     
        // check if sum of digits divides n
        if (temp % sum == 0)
            return "YES";
     
        return "NO";
    }
     
    // This is where the execution begins always (main function)
    public static void main(String []args)
    {
        long n = 123; // better to declare number here and give it as a parameter to function
        System.out.println(isDivisible(n)); // print the result of divisible or not
    }
}