UVa 583 Prime Factors Solution in Java

import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

/**
 * Created by dhruv.pancholi on 05/11/16.
 */
public class Main {

    public static List<Integer> getPrimeFactors(int N, List<Integer> primes) {
        List<Integer> factors = new ArrayList<Integer>();
        int index = 0;
        int factor = primes.get(index);
        int limit = (int) Math.sqrt(N) + 1;
        while (N != 1 && factor < limit) {
            while (N % factor == 0) {
                N /= factor;
                factors.add(factor);
            }
            factor = primes.get(++index);
        }
        if (N != 1) factors.add(N);
        return factors;
    }

    public static void main(String[] args) throws FileNotFoundException {
        InputReader in = new InputReader(System.in);

        SieveOfEratosthenes soe = new SieveOfEratosthenes((int) Math.sqrt(Integer.MAX_VALUE) * 10);
        List<Integer> primes = soe.getPrimes();


        int n;
        while (true) {
            n = in.nextInt();
            if (n == 0) break;
            List<Integer> factors = getPrimeFactors(Math.abs(n), primes);
            System.out.print(n + " = ");
            if (n < 0) System.out.print("-1 x ");
            for (int i = 0; i < factors.size() - 1; i++) {
                System.out.print(factors.get(i) + " x ");
            }
            System.out.println(factors.get(factors.size() - 1));
        }
    }

    private static class SieveOfEratosthenes {
        private boolean[] a;

        public SieveOfEratosthenes(int N) {
            a = new boolean[N + 1];
            for (int i = 0; i <= N; i++) {
                a[i] = true;
            }
            a[0] = false;
            a[1] = false;

            int root = (int) Math.sqrt(N);
            for (int i = 2; i <= root; i++) {
                for (int j = 2 * i; j <= N; j += i) {
                    a[j] = false;
                }
            }
        }

        public boolean[] getArray() {
            return a;
        }

        public boolean isPrime(int n) {
            return a[n];
        }

        public List<Integer> getPrimes() {
            List<Integer> list = new ArrayList<Integer>();
            for (int i = 1; i < a.length; i++) {
                if (a[i]) {
                    list.add(i);
                }
            }
            return list;
        }
    }

    public static class InputReader {
        private BufferedReader reader;
        private StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream));
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }
    }
}

Sample Input:

-190
-191
-192
-193
-194
195
196
197
198
199
200
0

Sample Output:

-190 = -1 x 2 x 5 x 19
-191 = -1 x 191
-192 = -1 x 2 x 2 x 2 x 2 x 2 x 2 x 3
-193 = -1 x 193
-194 = -1 x 2 x 97
195 = 3 x 5 x 13
196 = 2 x 2 x 7 x 7
197 = 197
198 = 2 x 3 x 3 x 11
199 = 199
200 = 2 x 2 x 2 x 5 x 5