This program runs the Sieve of Erathostenes benchmark : System « Development Class « Java

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This program runs the Sieve of Erathostenes benchmark

  
/*
   This program is a part of the companion code for Core Java 8th ed.
   (http://horstmann.com/corejava)

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

import java.util.*;

/**
 * This program runs the Sieve of Erathostenes benchmark. It computes all primes up to 2,000,000.
 * @version 1.21 2004-08-03
 * @author Cay Horstmann
 */
public class Sieve
{
   public static void main(String[] s)
   {
      int n = 2000000;
      long start = System.currentTimeMillis();
      BitSet b = new BitSet(n + 1);
      int count = 0;
      int i;
      for (i = 2; i <= n; i++)
         b.set(i);
      i = 2;
      while (i * i <= n)
      {
         if (b.get(i))
         {
            count++;
            int k = 2 * i;
            while (k <= n)
            {
               b.clear(k);
               k += i;
            }
         }
         i++;
      }
      while (i <= n)
      {
         if (b.get(i)) count++;
         i++;
      }
      long end = System.currentTimeMillis();
      System.out.println(count + " primes");
      System.out.println((end - start) + " milliseconds");
   }
}

   
    
  

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