Calculate the Number of Trailing Zeros in a Factorial

Solution.java

public class Solution {
    public static void main(String[] args) {
        System.out.println(countTrailingZerosOfFactorial(100));
    }
    
    private static final int countTrailingZerosOfFactorial(final int n) {
        int count = 0;
        for (int factor = 5; factor <= n; factor += 5)
            count += countFives(factor);
        return count;
    }

    private static final int countFives(int factor) {
        if (!divides(5, factor))
            return 0;

        return 1 + countFives(factor / 5);
    }
    
    private static final boolean divides(final int d, final int n) {
        return n % d == 0;
    }
}