IteratingProgram

package primeIteration;

import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;

public class PrimeFunctionIterate {

    public static void main(String[] args) {
        PrintWriter writ = null;
        try {
            writ = new PrintWriter("nums.txt", "UTF-8");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }

        for(int k=2; k < 10001; ++k){
            int num2 = 0;
            for(int i=1; i < k; ++i){
                int end = i;
                while(!(end < 10 && (isPrime(end) || end ==1))){
                    end = function(end);
                }
                if(end ==2) ++ num2;
            }
            double dub = (double)num2/(double)k;
            writ.println(dub);
        }
    }

    public static boolean isPrime(int n){
        for(int i=2; i < n/2+1; ++i){
            if(n % i == 0){
                return false;
            }
        }
        return true;
    }

    public static int function(int n){
        if(isPrime(n)){
            return sumDigits(n);
        }
        else return sumFactors(n);
    }

    public static int sumDigits(int n){
        String num = Integer.toString(n);
        int sum = 0;
        for(int i=0; i < num.length(); ++i){
            sum += Integer.parseInt(num.substring(i, i+1));
        }
        return sum;
    }

    public static ArrayList<Integer> factorList(int n){
        ArrayList<Integer> factors = new ArrayList<Integer>();
        if(isPrime(n)){
            ArrayList<Integer> single = new ArrayList<Integer>();
            single.add(n);
            return single;
        }

        for(int i=2; i < n/2; ++i){
            if(n % i == 0){
                factors.add(i);
                factors.addAll(factorList(n/i));
                break;
            }
        }

        return factors;
    }

    public static int sumFactors(int n){
        int sum = 0;
        ArrayList<Integer> factors = factorList(n);
        for(int i=0; i<factors.size(); ++i){
            sum += factors.get(i);
        }
        return sum;
    }

}