SieveOfEratosthenes

package me.andrew.unit10;

import java.util.*;

public class SieveOfEratosthenes {

    public SieveOfEratosthenes() {
    }

    public Set<Integer> populate(Set<Integer> set, int max) {
        for (int i = 2; i <= max; i++) {
            set.add(new Integer(i));
        }
        return set;
    }

    public Set<Integer> sieve(Set<Integer> set) {
        int max = set.size() + 1;
        boolean[] prime = new boolean[max + 1];
        for (int i = 2; i <= max; i++) {
            prime[i] = true;
        }
        for (int i = 2; i * i <= max + 1; i++) {
            if (prime[i]) {
                for (int j = i; i * j <= max; j++) {
                    prime[i * j] = false;
                }
            }
        }
        for (int i = 0; i < prime.length; i++) {
            if (prime[i] == false) {
                set.remove(new Integer(i));
            }
        }
        return set;
    }

    public void print(Set<Integer> set) {
        for (Integer i : set)
            System.out.println(i.toString());
    }

    public static void main(String[] args) {
        SieveOfEratosthenes test = new SieveOfEratosthenes();
        TreeSet<Integer> ts = new TreeSet<Integer>();
        long timeA = System.currentTimeMillis();
        test.populate(ts, 300000);
        test.sieve(ts);
        timeA = System.currentTimeMillis() - timeA;
        test.print(ts);
        HashSet<Integer> hs = new HashSet<Integer>();
        long timeB = System.currentTimeMillis();
        test.populate(hs, 300000);
        test.sieve(hs);
        timeB = System.currentTimeMillis() - timeB;
        test.print(hs);
        System.out.println("TreeSet time = " + timeA + "\nHashSet time = "
                + timeB);
    }
}