Review

class Primes {
    /**
     * Prime factors decomposition
     *
     * @param n number to factorize: must be ≥ 2
     * @return list of prime factors of n
     * @throws MathIllegalArgumentException if n < 2.
     */
    public static List<Integer> primeFactors(int n) {

        if (n < 2) {
            throw new MathIllegalArgumentException(LocalizedFormats.NUMBER_TOO_SMALL, n, 2);
        }
        // slower than trial div unless we do an awful lot of computation
        // (then it finally gets JIT-compiled efficiently
        // List<Integer> out = PollardRho.primeFactors(n);
        return SmallPrimes.trialDivision(n);

    }

}