class primesSeq { // Find all primes between 2 and N
   final static int PERLINE = 10;

   public static void main (String args[]) {
      int N = 100;
      boolean debug = false;
      try { N = Integer.parseInt(args[0]); }
      catch (ArrayIndexOutOfBoundsException e) {}
      catch (NumberFormatException e) {}
      try { debug = Boolean.valueOf(args[1]).booleanValue(); }
      catch (ArrayIndexOutOfBoundsException e) {}
      if (N < 2) { System.out.println("N < 2"); System.exit(-1); }
      boolean[] isPrime = new boolean[N+1];  // 1..N rather than 0..N-1
      for (int i=0; i<=N; i++) isPrime[i] = true;
      int crossingOutPrime = 2;
      int crossingOutSquared = 4;
      //    int finalCross = (int)(Math.floor(Math.sqrt((double)N)));
      int numPrimes = 0;
      System.out.println("Find all primes between 2 and " + N);
      while (crossingOutSquared <= N) {
         // cross out all multiples of this prime
         for (int i = crossingOutSquared; i<=N; i=i+crossingOutPrime) {
            isPrime[i] = false;
         }
         while (!isPrime[++crossingOutPrime]) {}  // advance to next prime
         crossingOutSquared = crossingOutPrime*crossingOutPrime;
      }
      for (int i=2; i<=N; i++) {
         if (isPrime[i]) { numPrimes++;
            if (debug) {
              System.out.print(" " + i);
              if ((numPrimes % PERLINE) == 0) System.out.print("\n");
            }
         }
      }
      if (debug) if ((numPrimes % PERLINE) != 0) System.out.print("\n");
      System.out.println("There are " + numPrimes + " in this range");
   }
}

/* ............... Example compile and run(s)

% uname -a
SunOS cheshire 5.4 Generic_101945-32 sun4m sparc
% $JAVAHOME/bin/javac primesSeq.java
% $JAVAHOME/bin/java primesSeq 100 true
Find all primes between 2 and 100
 2 3 5 7 11 13 17 19 23 29
 31 37 41 43 47 53 59 61 67 71
 73 79 83 89 97
There are 25 in this range
% time $JAVAHOME/bin/java primesSeq 1000
Find all primes between 2 and 1000
There are 168 in this range
0.0u 1.0s 0:02 39% 0+0k 0+0io 0pf+0w
% time $JAVAHOME/bin/java primesSeq 10000
Find all primes between 2 and 10000
There are 1229 in this range
1.0u 1.0s 0:02 76% 0+0k 0+0io 0pf+0w
% time $JAVAHOME/bin/java primesSeq 100000
Find all primes between 2 and 100000
There are 9592 in this range
3.0u 1.0s 0:05 75% 0+0k 0+0io 0pf+0w
% time $JAVAHOME/bin/java primesSeq 1000000
Find all primes between 2 and 1000000
There are 78498 in this range
30.0u 1.0s 0:32 95% 0+0k 0+0io 0pf+0w
% time $JAVAHOME/bin/java primesSeq 10000000
Find all primes between 2 and 10000000
There are 664579 in this range
316.0u 2.0s 5:20 99% 0+0k 0+0io 0pf+0w
                                              */