// CSE 142, Winter 2008, Marty Stepp
//
// This program computes prime numbers.  This is an updated version of a
// program we wrote previously, updated to use an isPrime method that
// returns a boolean result.

public class Primes2 {
	public static void main(String[] args) {
		printPrimes(50);
		printPrimes(1000);
		printPrimes(1);
	}
	
	public static void printPrimes(int max) {
		System.out.print("[");
		if (max >= 2) {
			System.out.print(2);
			for (int i = 3; i <= max; i++) {
				// new code
				if (isPrime(i)) {
					System.out.print(", " + i);
				}
			}
		}
		System.out.println("]");
	}
	
	// new code
	// Returns true if n is prime, and false if not.
	public static boolean isPrime(int n) {
		if (countFactors(n) == 2) {
			return true;
		} else {
			return false;
		}
	}

	// Returns the number of factors of the given integer.
	// Assumes that a non-negative number is passed.
	public static int countFactors(int number) {
		int count = 0;
		for (int i = 1; i <= number; i++) {
			if (number % i == 0) {
				// i is a factor of the number
				count++;
			}
		}

		return count;
	}
}