class Find400Primes {
    public static void main(String arguments[]) {
        int[] primes = new int[400];
        int numPrimes = 0;
        // candidate: the number that might be prime
        int candidate = 2;
        while (numPrimes < 400) {
            if (isPrime(candidate)) {
                primes[numPrimes] = candidate;
                numPrimes++;
            }
            candidate++;
        }
        System.out.println("First 400 primes:");
        for (int i = 0; i < 400; i++)
           System.out.print(primes[i] + " ");
    }

    public static boolean isPrime(int checkNumber) {
        double root = Math.sqrt(checkNumber); 
        // check every number from 2 to the square
        // root of checkNumber, to see if any of them
        // produce a remainder of 0 when checkNumber
        // is divided by the number
        //   Any have a remainder of 0? Not prime
        //   None? Prime
        for (int i = 2; i <= root; i++) {
            if (checkNumber % i == 0)
                return false;
        }
        return true;
    }
}