Question

Write a recursive function called sumDigits with the following signature: public static long sumDigits(long n) that computes the sum of the digits in a number repeatedly, until the sum is a single digit. For example, if we call sumDigits(123456), the following would result: sumDigits(123456) => 1+2+3+4+5+6 => 21 => 2+1 => 3 so the final answer would be 3. You must meaningfully use recursion for this lab in order to receive any credit. Hint: For this problem it might be useful to convert back and forth between longs and strings. This can be done using the Long.parseLong method and the Long.toString method.

Answer 1

Here you go:

public static long sumDigits(long n) {

if (n < 10) {

return n; // our exit criterion

}

String str = Long.toString(n);

long sum = 0;

for(int i=0; i<str.length(); i++) {

sum += Character.getNumericValue(str.charAt(i));

}

return sumDigits(sum);

}