204 Count Primes

Description:

Count the number of prime numbers less than a non-negative number, n.

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