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Groovy example source code file (nsievebits.java)

This example Groovy source code file (nsievebits.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Groovy tags/keywords

bitset, bitset, string, string, stringbuffer, stringbuffer, util

The Groovy nsievebits.java source code

/* The Computer Language Shootout
http://shootout.alioth.debian.org/

contributed by Alkis Evlogimenos
*/

import java.util.BitSet;

public class nsievebits
{
   private static int nsieve(int m, BitSet bits) {
      bits.set(0, m+1);

      int count = 0;
      for (int i = 2; i <= m; ++i) {
         if (bits.get(i)) {
         for (int j = i + i; j <=m; j += i)
            bits.clear(j);
            ++count;
         }
      }
      return count;
   }

   public static String padNumber(int number, int fieldLen)
   {
      StringBuffer sb = new StringBuffer();
      String bareNumber = "" + number;
      int numSpaces = fieldLen - bareNumber.length();

      for (int i = 0; i < numSpaces; i++)
         sb.append(" ");

      sb.append(bareNumber);

      return sb.toString();
   }

   public static void main(String[] args)
   {
      int n = 2;
      if (args.length > 0)
         n = Integer.parseInt(args[0]);
      if (n < 2)
         n = 2;

      int m = (1 << n) * 10000;
      BitSet bits = new BitSet(m+1);
      System.out.println("Primes up to " + padNumber(m, 8) + " " + padNumber(nsieve(m,bits), 8));

      m = (1 << n-1) * 10000;
      System.out.println("Primes up to " + padNumber(m, 8) + " " + padNumber(nsieve(m,bits), 8));

      m = (1 << n-2) * 10000;
      System.out.println("Primes up to " + padNumber(m, 8) + " " + padNumber(nsieve(m,bits), 8));
   }
}

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