UVa 406 Prime Cuts Solution in Java

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

public class PrimeCuts {
    public static void main(String[] args) {
        InputReader in = new InputReader(System.in);
        SieveOfEratosthenes soe = new SieveOfEratosthenes(1000);
        boolean[] arr = soe.getArray();
        arr[1] = true;
        int[] agg = new int[1001];
        for (int i = 1; i < agg.length; i++) {
            agg[i] += agg[i - 1];
            if (arr[i]) agg[i]++;
        }

        while (true) {
            int n = in.nextInt();
            int c = in.nextInt();
            int startIndex = (agg[n] % 2 == 0) ? (agg[n] / 2) : (agg[n] / 2 + 1);
            startIndex -= (c - 1);
            startIndex = startIndex > 0 ? startIndex : 1;
            int endIndex = startIndex + ((agg[n] % 2 == 0) ? (2 * c - 1) : (2 * c - 2));
            endIndex = endIndex > n ? n : endIndex;

            System.out.print(n + " " + c + ":");
            int index = 0;
            for (int i = 1; i <= n; i++) {

                if (arr[i]) {
                    index++;
                    if (index >= startIndex && index <= endIndex) {
                        System.out.print(" " + i);
                    }
                }
            }
            System.out.println();
            System.out.println();
        }
    }

    public 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 (Exception e) {
                    System.exit(0);
                }
            }
            return tokenizer.nextToken();
        }

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

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

Sample Input:

21 2
18 2
18 18
100 7

Sample Output:

21 2: 5 7 11

18 2: 3 5 7 11

18 18: 1 2 3 5 7 11 13 17

100 7: 13 17 19 23 29 31 37 41 43 47 53 59 61 67