204. Count Primes

class Solution {
    public int countPrimes(int n) {
        int count = 0;
        for (int i = 2; i < n; i++){
            if (isPrime(i)) count++;
        }
        return count;
    }
    public boolean isPrime(int n){
        for (int i = 2; i*i <= n; i++){
            if ( n % i == 0) return false;
        }
        return true;
    }
}