Primey 2

package funtimes;

import java.util.ArrayList;

public class Primes {
    public static void main(String[] args) {
        int length = 100000;
        ArrayList<Integer> composite = new ArrayList<>();
        ArrayList<Integer> primes = new ArrayList<>();
        System.out.println("Primes up to " + length + " are:");
        for (int num = 1; num <= length; ++num) {
            checkPrime(primes, composite, num);
        }
    }

    private static void checkPrime(ArrayList<Integer> primes, ArrayList<Integer> composite, int num) {
        for (int i = 1; i < primes.size(); ++i) {
            if (num % primes.get(i) == 0) {
                composite.add(num);
                return;
            }
        }
        findPrime(primes, composite, num);
    }

    private static void findPrime(ArrayList<Integer> primes, ArrayList<Integer> composite, int num) {
        for (int div = 2; div < composite.size(); ++div) {
            if (div > composite.get(div) || num % composite.get(div) == 0) {
                composite.add(num);
                return;
            }
        }
        primes.add(num);
        System.out.println(num);
    }
}